Math
2023-01-05 21:59:48 3 举报AI智能生成
数二
人工智能
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大纲/内容
函数、极限、连续
函数
奇偶性
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x)是奇(偶)函数=>f'(x)是偶(奇)函数" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="连续的奇函数的原函数是偶函数" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="连续的偶函数的原函数只有一个是奇函数" style=""><span></span><span></span></span>(<span class="equation-text" data-index="1" data-equation="\int{x^2dx}=\frac{1}{3}x^3+C(当C是0的时候原函数才是偶函数)" style="" contenteditable="false"><span></span><span></span></span>)
周期性
<span class="equation-text" contenteditable="false" data-index="0" data-equation="可导周期函数的导函数一定为周期函数" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="周期函数的原函数不一定是周期函数"><span></span><span></span></span>(<span class="equation-text" data-index="1" data-equation="1+\cos{x}" style="" contenteditable="false"><span></span><span></span></span>)
有界性
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f'(x)有界 \implies f(x)有界" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="在[a,b]上连续 \implies 在[a,b]上有界" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="在(a,b)上连续,且f(a^+)和f(b^-)存在 \implies 在(a,b)上有界" style=""><span></span><span></span></span>
极限(李4第二套第一题!!!)
性质
<span class="equation-text" contenteditable="false" data-index="0" data-equation="局部有界性:若极限存在,则f(x)在点x_0某去心领域内有界" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="保号性"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="A>0 \implies f(x)>0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x)\ge 0 \implies A \ge 0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="脱帽法"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\lim f(x)=A \iff f(x)=A+\alpha(x),其中\lim\alpha(x)=0" style=""><span></span><span></span></span>
存在准则
<span class="equation-text" contenteditable="false" data-index="0" data-equation="夹逼准则" style=""><span></span><span></span></span><br>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="单调有界准则" style=""><span></span><span></span></span>
极限计算
<span class="equation-text" contenteditable="false" data-index="0" data-equation="夹逼准则(分母或者分子变化,不要分子分母都变化)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="S_n = \lim_{n\to\infty}\frac{1}{n^2+n+1}+\frac{2}{n^2+n+2}+...+\frac{n}{n^2+n+n}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\frac{1+2+...+n}{n^2+n+1}\geq S_n \geq \frac{1+2+...+n}{n^2+n+n}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="黎曼积分"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="单调有界准则"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="各种类型"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\frac{0}{0}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\frac{\infty}{\infty}" style=""><span></span><span></span></span>
洛必达
分子分母同除以最高阶的无穷大
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\infty-\infty" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="化为\frac00" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="根式有理化(用于根式差)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="提无穷因子,然后等价代换或变量代换(\frac{1}{t})、泰勒公式" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="n项和的数列极限" style=""><span></span><span></span></span>
夹逼定理
定积分定义
<span class="equation-text" contenteditable="false" data-index="0" data-equation="n项连乘的数列极限" style=""><span></span><span></span></span>
夹逼原理
取对数化为n项和
<span class="equation-text" contenteditable="false" data-index="0" data-equation="递推关系,x_1=a,x_{n+1}=f(x_n)定义的数列" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="先证数列收敛(单调有界准则),然后令\lim_{x\to \infty }=A,等式x_{n+1}=f(x_n),两端取极限得A=f(A),由此求得极限A"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="跟上面反过来,直接求A,然后证明\lim_{n \to \infty}x_n=A" style=""><span></span><span></span></span>
连续
连续定义
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x_0)连续 \iff f(x_0)左连续且右连续(左导和右导存在且相等)" style=""><span></span><span></span></span>
<font color="#81c784">间断点(不连续必定不可导!!!)</font>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="第一类间断点(左、右极限存在)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="可去间断点:左、右极限存在且相等,无定义点"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="跳跃间断点:左、右极限存在但不相等" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="第二类间断点(左、右至少一个不存在)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="无穷间断点:左、右极限至少一个为无穷,无定义点"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="振荡间断点:\sin(\frac1x)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="在第一类间断点中,有两种情况,左右极限存在是前提。左右极限相等,但不等于该点函数值f(x0)或者该点无定义时,"><span></span><span></span></span><span class="equation-text" contenteditable="false" data-index="1" data-equation="称为可去间断点"><span></span><span></span></span>
连续函数性质
<span class="equation-text" contenteditable="false" data-index="0" data-equation="有界性"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="最值性"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="介值性"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="零点定理: f(a)*f(b)<0"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="找间断点"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="找整体函数无意义点,还有局部函数无意义点和间断点"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x)连续,\psi(x)有间断点,两者加减乘除后的函数是可能存在间断点的" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="比如\frac{(x+1)|x-1|}{e^{\frac{1}{x-2}}ln|x|}" style=""><span></span><span></span></span>0<span class="equation-text" contenteditable="false" data-index="1" data-equation=",存在的间断点有0(为ln|x|的间断点),1,-1,2"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="偶函数的间断点对称"><span></span><span></span></span>
基本不等式
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\frac{x}{1+x}<ln(1+x)<x" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mfrac><mi>x</mi><mrow><mn>1</mn><mo>+</mo><mi>x</mi></mrow></mfrac><mo><</mo><mi>l</mi><mi>n</mi><mo>(</mo><mn>1</mn><mo>+</mo><mi>x</mi><mo>)</mo><mo><</mo><mi>x</mi></mrow><annotation encoding="application/x-tex">\frac{x}{1+x}<ln(1+x)<x</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.0987230000000001em;vertical-align:-0.403331em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.695392em;"><span style="top:-2.655em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">1</span><span class="mbin mtight">+</span><span class="mord mathdefault mtight">x</span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.394em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathdefault mtight">x</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.403331em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel"><</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathdefault" style="margin-right:0.01968em;">l</span><span class="mord mathdefault">n</span><span class="mopen">(</span><span class="mord">1</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathdefault">x</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel"><</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord mathdefault">x</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\sqrt{ab}\leq\frac{a+b}{2}\leq\sqrt{\frac{a^2+b^2}{2}}" style=""><span></span><span></span></span>(当a=b时,等式成立)
<span class="equation-text" contenteditable="false" data-index="0" data-equation="e^x>1+x" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="a^3-b^3=(a-b)(a^2+ab+b^2)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="a^3+b^3=(a+b)(a^2-ab+b^2)" style=""><span></span><span></span></span>
极坐标方程
<span class="equation-text" contenteditable="false" data-index="0" data-equation="r=\sqrt{x^2+y^2}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="dxdy=rdrd\theta" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="(r,\theta)|0\le r \le \sec{\theta},0\le\theta\le\frac{\pi}{4}\implies(x,y)|x=1,y=x,x=0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="若r=2a\cos{\theta},两边同乘以r得,r^2=2a\cos{\theta}r=2ax,从而求出直角坐标系下的圆方程!!!" style=""><span></span><span></span></span>
<font color="#ffffff">微分</font>
导数
<span class="equation-text" contenteditable="false" data-index="0" data-equation="可导 \iff 左、右导数都存在且相等" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f'(x)=\lim_{\triangle x \to 0}\frac{f(x_0+\triangle x)-f(x_{0})}{\triangle x}=\lim_{x\to x_0}\frac{f(x)-f(x_0)}{x-x_0}" style=""><span></span><span></span></span>
可微
<span class="equation-text" contenteditable="false" data-index="0" data-equation="dy=f'(x_0)dx" style=""><span></span><span></span></span>
关系
<span class="equation-text" contenteditable="false" data-index="0" data-equation="连续推不出可导f(x)=|x|,可导推不出导函数连续x^2\sin{\frac1x}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="使用洛必达注意事项(需要n阶导函数连续)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="(1)f(x)n阶可导 \implies f^{(n-1)}(x)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="(2)f(x)n阶可导连续 \implies f^n(x)" style=""><span></span><span></span></span>
高阶导数计算
归纳法
泰勒公式(用于求特定点的高阶导数),泰勒展开后,找到<span class="equation-text" contenteditable="false" data-index="0" data-equation="x^n" style=""><span></span><span></span></span>的系数,系数等于<span class="equation-text" contenteditable="false" data-index="1" data-equation="\frac{f^{n}(x_{0})}{n!}" style=""><span></span><span></span></span>,即可求得<span class="equation-text" contenteditable="false" data-index="2" data-equation="f^n(x_{0})" style=""><span></span><span></span></span>
利用现有高阶导数公式,<span class="equation-text" contenteditable="false" data-index="0" data-equation="(\sin{x})^n=\sin{(x+n*\frac{\pi}{2})}"><span></span><span></span></span>,<span class="equation-text" contenteditable="false" data-index="1" data-equation="(\cos{x})^n=\cos{(x+n*\frac{\pi}{2})}"><span></span><span></span></span>,<span class="equation-text" contenteditable="false" data-index="2" data-equation="(uv)^n=\sum_{k=0}^nC^k_{n}u^{(n-k)}v^k"><span></span><span></span></span>
特殊函数求导
<span class="equation-text" contenteditable="false" data-index="0" data-equation="(ln|x|)'=\frac1x(当x<0时,\ln |x|=\ln{-x},这时候要看成复合函数进行求导)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="分段函数在分界点处的导数一般用定义求导" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="存在+存在=存在,不存在+存在=不存在,不存在+不存在=不好说" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x)f'(x)=\frac12[f(x)^2]'" style=""><span></span><span></span></span>
微分中值定理
<span class="equation-text" contenteditable="false" data-index="0" data-equation="罗尔定理 : f(a)=f(b)\implies f'(\xi)=0"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="拉格朗日定理, f(x_0)-f(x_1)的情况!!!!"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="柯西定理:g'(x) \neq 0 \implies \frac{f(b)-f(a)}{g(b)-g(a)}=\frac{f'(\xi)}{g'(\xi)}"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="泰勒公式(拉格朗日余项):余项R_n(x)为\frac{f^{n+1}(\xi)}{(n+1)!}(x-x_0)^{n+1},\xi在x和x_0之间"><span></span><span></span></span>
极值
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f'(x)=0" style=""><span></span><span></span></span>(驻点和不可导点)
<span class="equation-text" contenteditable="false" data-index="0" data-equation="充分条件" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="(1)f'(x_0)=0 且在x_0领域内f'(x_0)变号可得极大极小值(可能不变号)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="(2)f'(x_o)=0,f''(x_o) \neq0"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="(3)f'(x_0)=f''(x_0)=...=f^{n-1}(x_0)=0,f^{n}\neq 0,f^{n}(x_0)>0极小,n为偶数" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="最值就是找驻点和边界点" style=""><span></span><span></span></span>
曲线的凹凸
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f''(x_0)=0不一定为拐点,还必须保证f''(x_0)左右变号(即f^3(x_0)\neq0)"><span></span><span></span></span>
渐近线
<span class="equation-text" contenteditable="false" data-index="0" data-equation="水平渐近线:\lim_{x\to \infty}=A"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="垂直渐近线:\lim_{x \to x_0}=\infty" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="斜渐近线:\lim_{x \to \infty}\frac{f(x)}{x}=a,\lim_{x\to\infty}f(x)-ax=b"><span></span><span></span></span>
曲率
<span class="equation-text" contenteditable="false" data-index="0" data-equation="K=\frac{|y''|}{(1+y'^2)^{\frac32}}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="曲率半径:\frac1K" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="曲率越大,曲线弯曲程度越大"><span></span><span></span></span>
题型
<span class="equation-text" contenteditable="false" data-index="0" data-equation="方程根的存在和个数"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="存在性"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="零点定理"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="罗尔定理"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="根的个数"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="单调性:要注意边界的极限值(即零点定理)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="罗尔定理推论:若f^n(x)\neq0,方程f(x)=0在I上最多有n个实根(可由反证法证明)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="证明函数不等式(单最泰拉凹)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="单调性" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="最大最小值" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="拉格朗日中值定理" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="泰勒公式" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="凹凸性" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="微分中值定理证明"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="证明存在一个点\xi,使得F[\xi,f(\xi),f'(\xi)]=0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="罗尔定理,找到g'(x)=F(x),通过g(a)=g(b)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="微分方程:核心思想——遇到f'(\xi)+g(\xi)f(\xi)=0(没有这种格式就创造他),直接F(x)=e^{\int g(x)dx}f(x)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="零点定理" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="证明存在两个中值点\xi,\eta,使F[\xi,\eta,f(\xi),f(\eta),f'(\xi),f'(\eta)]=0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="不要求\xi \neq \eta:直接两次拉格朗日或者柯西" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="要求\xi \neq \eta:分区间用拉格朗日" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="证明存在一个中值点\xi,使F[\xi,f^n(\xi)]=0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="看到f^n(x),不管哪种题,优先考虑泰勒公式,找函数值多的那个点" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="泰勒公式"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="莱布尼茨公式"><span></span><span></span></span>
积分
不定积分
概念
+C +C +C 记得+C
存在性
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x)连续 \implies 必有原函数" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x)有第一类间断点 \implies 必没原函数" style=""><span></span><span></span></span>
基本不定积分
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int a^x dx=\frac{a^x}{lna}+C" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mo>∫</mo><msup><mi>a</mi><mi>x</mi></msup><mi>d</mi><mi>x</mi><mo>=</mo><mfrac><msup><mi>a</mi><mi>x</mi></msup><mrow><mi>l</mi><mi>n</mi><mi>a</mi></mrow></mfrac><mo>+</mo><mi>C</mi></mrow><annotation encoding="application/x-tex">\int a^x dx=\frac{a^x}{lna}+C</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.11112em;vertical-align:-0.30612em;"></span><span class="mop op-symbol small-op" style="margin-right:0.19445em;position:relative;top:-0.0005599999999999772em;">∫</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord"><span class="mord mathdefault">a</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.664392em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathdefault mtight">x</span></span></span></span></span></span></span></span><span class="mord mathdefault">d</span><span class="mord mathdefault">x</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1.25598em;vertical-align:-0.345em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.91098em;"><span style="top:-2.6550000000000002em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathdefault mtight" style="margin-right:0.01968em;">l</span><span class="mord mathdefault mtight">n</span><span class="mord mathdefault mtight">a</span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.394em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight"><span class="mord mathdefault mtight">a</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.7385428571428572em;"><span style="top:-2.931em;margin-right:0.07142857142857144em;"><span class="pstrut" style="height:2.5em;"></span><span class="sizing reset-size3 size1 mtight"><span class="mord mathdefault mtight">x</span></span></span></span></span></span></span></span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.68333em;vertical-align:0em;"></span><span class="mord mathdefault" style="margin-right:0.07153em;">C</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int \sec{x}dx=\ln|\sec x + \tan x|+C" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int \frac{1}{a^2+x^2}dx=\frac1{a}\arctan{\frac xa}+C" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int \frac{1}{a^2-x^2}dx=\frac 1{2a}\ln{|\frac{a+x}{a-x}|}+C" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int\frac{1}{\sqrt{ a^2-x^2}}dx=\arcsin{\frac xa}+C" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int \frac{1}{\sqrt{x^2+a^2}}=\ln{|x+\sqrt{x^2+a^2}|}+C" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int \frac{1}{\sqrt{x^2-a^2}}=\ln{|x+\sqrt{x^2-a^2}|}+C" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="万能公式\tan\frac{x}{2}=t \implies \sin x = \frac{2t}{1+t^2},\cos x=\frac{1-t^2}{1+t^2}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="看到没办法的,直接多次分部试试" style=""><span></span><span></span></span>
定积分
定义
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int_a^bf(x)dx=lim_{n\to\infty}\sum_{i=1}^n f(a+\frac{b-a}{n}i)\frac{b-a}{n},看\frac in变化到多大" style=""><span></span><span></span></span>
性质
<span class="equation-text" contenteditable="false" data-index="0" data-equation="若f(x) \leq g(x),则\int_a^bf(x)dx \leq \int_a^bg(x)dx" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="m(b-a) \leq \int^b_af(x)dx\leq M(b-a)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="|\int^b_af(x)dx|\leq \int^b_a|f(x)|dx" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="积分中值定理:\int^b_af(x)dx=f(\xi)(b-a)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="广义积分中值定理:g(x)不变号,\int^b_af(x)g(x)dx=f(\xi)\int_a^bg(x)dx" style=""><span></span><span></span></span>
题型
<span class="equation-text" contenteditable="false" data-index="0" data-equation="三角函数"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="解\int\frac{Csinx +Dcosx}{Asinx+Bcosx}这种由三角函数线性组成的分子式,可用\int\frac{A(分母负数)+B(分母)}{分母}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="区间再现公式x=a+b-t(被积函数的原函数不易求出时考虑)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="对称区间,函数奇偶性" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="根号内配方,\int x\sqrt{2x-x^2}=\int x\sqrt{1-(x-1)^2}\to^{x-1=\sin t}=\int (\sin t+1)\cos t" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="变上限积分" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="若f(x)为偶函数,则\int^x_af(x)dx为奇函数\\若f(x)为奇函数,则\int^x_af(x)dx为偶函数" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="变上限积分有关极限问题(洛等积广)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="洛必达"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="等价无穷小(若\lim_{x\to\infty}\frac{f(x)}{g(x)}=1,则\int_0^xf(x)\sim \int_0^xg(x) )"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="积分中值定理(广义积分中值定理)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="积分不等式(定换变积柯)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="定积分不等式性质"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="变量代换(上下限不同)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="变上限积分"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="积分中值定理(上下限不同)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="柯西积分不等式(\int^b_af(x)g(x)dx)^2 \leq \int^b_af^2(x)dx\int^b_ag^2(x)dx"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f(x)=\int_0^xf'(t)dt(f(0)=0的条件下)" style=""><span></span><span></span></span>
特殊
<span class="equation-text" contenteditable="false" data-index="0" data-equation="结论:\int^{g(x)}_0f(t)dt,f(x)和g(x)分别是x的n阶、m阶次无穷小,则当x\to0时,\int^{g(x)}_0f(t)dt是x的n(m+1)阶无穷小" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="I_1,I_2,I_3的大小比较"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="定积分性质:若f(x) \leq g(x),则\int_a^bf(x)dx \leq \int_a^bg(x)dx,特殊的g(x)=1" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="区间如果为对称区间,用函数奇偶性" style=""><span></span><span></span></span>
反常积分(分段讨论)
无穷区间
<span class="equation-text" contenteditable="false" data-index="0" data-equation="比较判别法 0\leq f(x)\leq g(x)"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="比较法的极限形式 \lim_{x\to\infty}\frac{f(x)}{g(x)}=A"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int^{+\infty}_0\frac{1}{x^p}\left\{<br>\begin{aligned}<br>&p>1,收敛\\<br>&p\leq1,发散<br>\end{aligned}<br>\right." style=""><span></span><span></span></span>
无界函数
<span class="equation-text" contenteditable="false" data-index="0" data-equation="比较判别法"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="比较法的极限形式"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int^{b}_a\frac{1}{(x-a)^p}\left\{<br>\begin{aligned}<br>&p<1,收敛\\<br>&p\geq1,发散<br>\end{aligned}<br>\right." style=""><span></span><span></span></span>
加减乘除
<span class="equation-text" contenteditable="false" data-index="0" data-equation="相加/减:收敛,极限为原两函数极限之和/差" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="相乘:收敛,极限为原两函数极限之积" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="相除" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="分子极限为非零值,分母极限为零则发散(极限为无穷大)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="分子,分母极限都为零则可能发散也可能收敛,若分子是比分母高阶的无穷小则收敛于0,\\若分子与分母同阶则收敛于非零值,若分子比分母低阶则发散"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="分母极限为非零值,无论分子极限是多少,结果都收敛,极限为两函数之商" style=""><span></span><span></span></span>
万能公式(无敌)
<span class="equation-text" contenteditable="false" data-index="0" data-equation="核心思想:等价转换为下面的标准型" style=""><span></span><span></span></span>
积分应用
<span class="equation-text" contenteditable="false" data-index="0" data-equation="做功:PgVh" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="压强:PgSh" style=""><span></span><span></span></span>
微分方程
一阶微分
<span class="equation-text" contenteditable="false" data-index="0" data-equation="可分离变量"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="齐次方程(\frac{y}{x})"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="线性方程:e^{-\int p(x)}[\int{ e^{p(x)}q(x)}+C]" style=""><span></span><span></span></span>
可降阶微分
<span class="equation-text" contenteditable="false" data-index="0" data-equation="缺y型:p=y',p'=y''" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">缺</mi><mi>y</mi><mi mathvariant="normal">型</mi><mi mathvariant="normal">:</mi><mi>p</mi><mo>=</mo><msup><mi>y</mi><mo mathvariant="normal">′</mo></msup><mi mathvariant="normal">,</mi><msup><mi>p</mi><mo mathvariant="normal">′</mo></msup><mo>=</mo><msup><mi>y</mi><mrow><mo mathvariant="normal">′</mo><mo mathvariant="normal">′</mo></mrow></msup></mrow><annotation encoding="application/x-tex">缺y型:p=y',p'=y''</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord cjk_fallback">缺</span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mord cjk_fallback">型</span><span class="mord cjk_fallback">:</span><span class="mord mathdefault">p</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.946332em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.751892em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">′</span></span></span></span></span></span></span></span></span><span class="mord cjk_fallback">,</span><span class="mord"><span class="mord mathdefault">p</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.751892em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">′</span></span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.946332em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.751892em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">′</span><span class="mord mtight">′</span></span></span></span></span></span></span></span></span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="缺x型:p=y',p'=p\frac{dp}{dy}" style=""><span></span><span></span></span>
高阶微分
<span class="equation-text" contenteditable="false" data-index="0" data-equation="齐次方程 \ \ \ \ \ \ y''+p(x)y'+q(x)y=0\ \ \ \ \ \ (1)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="非齐次方程 \ \ y''+p(x)y'+q(x)y=f(x)(2)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="定理(线性无关就是比值不为常数)" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">定</mi><mi mathvariant="normal">理</mi><mi mathvariant="normal">(</mi><mi mathvariant="normal">线</mi><mi mathvariant="normal">性</mi><mi mathvariant="normal">无</mi><mi mathvariant="normal">关</mi><mi mathvariant="normal">就</mi><mi mathvariant="normal">是</mi><mi mathvariant="normal">比</mi><mi mathvariant="normal">值</mi><mi mathvariant="normal">不</mi><mi mathvariant="normal">为</mi><mi mathvariant="normal">常</mi><mi mathvariant="normal">数</mi><mi mathvariant="normal">)</mi></mrow><annotation encoding="application/x-tex">定理(线性无关就是比值不为常数)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0em;vertical-align:0em;"></span><span class="mord cjk_fallback">定</span><span class="mord cjk_fallback">理</span><span class="mord cjk_fallback">(</span><span class="mord cjk_fallback">线</span><span class="mord cjk_fallback">性</span><span class="mord cjk_fallback">无</span><span class="mord cjk_fallback">关</span><span class="mord cjk_fallback">就</span><span class="mord cjk_fallback">是</span><span class="mord cjk_fallback">比</span><span class="mord cjk_fallback">值</span><span class="mord cjk_fallback">不</span><span class="mord cjk_fallback">为</span><span class="mord cjk_fallback">常</span><span class="mord cjk_fallback">数</span><span class="mord cjk_fallback">)</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="y_1(x)和y_2(x)是齐次方程(1)的两个线性无关的特解,那么\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ y=C_1y_1(x)+C_2y_2(x)\\就是方程(1)的通解" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="y^*是非齐次方程(2)的特解,y_1(x)和y_2(x)是齐次方程(1)的两个线性无关的特解,则\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ y=y^*+C_1y_1(x)+C_2y_2(x)(x)\\是非齐次方程(2)的通解" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="如果y^*_1(x)和y^*_2(x)是非齐次方程(2)的两个特解,则\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ y(x)=y^*_2(x)-y^*_1(x)\\是齐次方程(1)的解" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="如果y^*_1(x),y^*_2(x)分别是方程\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ y''+p(x)y'+q(x)y=f_1(x)\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ y''+p(x)y'+q(x)y=f_2(x)\\的特解,则y^*_1(x)+y^*_2(x)是方程\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ y''+p(x)y'+q(x)y=f_1(x)+f_2(x)\\的一个特解" style=""><span></span><span></span></span>
题型
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P143 例1"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P144 例2 :注意丢解的情况,如\frac{u}{1-u^2}du=\frac1ydy,这里u为自变量,所以要考虑u=1和-1的情况" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P149 例1" style=""><span></span><span></span></span>
多元函数
重极限
常用方法
<span class="equation-text" contenteditable="false" data-index="0" data-equation="利用极限的性质" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="四则运算法则" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="夹逼定理"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="局部有界性" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="保号性" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="消去分母中极限为零的因子(有理化,等价无穷小代换)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="利用无穷小量与有界变量之积为无穷小量" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">利</mi><mi mathvariant="normal">用</mi><mi mathvariant="normal">无</mi><mi mathvariant="normal">穷</mi><mi mathvariant="normal">小</mi><mi mathvariant="normal">量</mi><mi mathvariant="normal">与</mi><mi mathvariant="normal">有</mi><mi mathvariant="normal">界</mi><mi mathvariant="normal">变</mi><mi mathvariant="normal">量</mi><mi mathvariant="normal">之</mi><mi mathvariant="normal">积</mi><mi mathvariant="normal">为</mi><mi mathvariant="normal">无</mi><mi mathvariant="normal">穷</mi><mi mathvariant="normal">小</mi><mi mathvariant="normal">量</mi></mrow><annotation encoding="application/x-tex">利用无穷小量与有界变量之积为无穷小量</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0em;vertical-align:0em;"></span><span class="mord cjk_fallback">利</span><span class="mord cjk_fallback">用</span><span class="mord cjk_fallback">无</span><span class="mord cjk_fallback">穷</span><span class="mord cjk_fallback">小</span><span class="mord cjk_fallback">量</span><span class="mord cjk_fallback">与</span><span class="mord cjk_fallback">有</span><span class="mord cjk_fallback">界</span><span class="mord cjk_fallback">变</span><span class="mord cjk_fallback">量</span><span class="mord cjk_fallback">之</span><span class="mord cjk_fallback">积</span><span class="mord cjk_fallback">为</span><span class="mord cjk_fallback">无</span><span class="mord cjk_fallback">穷</span><span class="mord cjk_fallback">小</span><span class="mord cjk_fallback">量</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="用y=kx等方式证明极限不存在" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\frac00同阶一般极限不存在" style=""><span></span><span></span></span>
题型
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\lim_{(x,y)\to(0,0)}\frac{x^2y}{x^2+y^2}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="x^2y比x^2+y^2高阶,一般极限不存在,解法:加0\leq|绝对值|,然后夹逼" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><msup><mi>x</mi><mn>2</mn></msup><mi>y</mi><mi mathvariant="normal">比</mi><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><msup><mi>y</mi><mn>2</mn></msup><mi mathvariant="normal">高</mi><mi mathvariant="normal">阶</mi><mi mathvariant="normal">,</mi><mi mathvariant="normal">一</mi><mi mathvariant="normal">般</mi><mi mathvariant="normal">极</mi><mi mathvariant="normal">限</mi><mi mathvariant="normal">不</mi><mi mathvariant="normal">存</mi><mi mathvariant="normal">在</mi><mi mathvariant="normal">,</mi><mi mathvariant="normal">解</mi><mi mathvariant="normal">法</mi><mi mathvariant="normal">:</mi><mi mathvariant="normal">加</mi><mn>0</mn><mo>≤</mo><mi mathvariant="normal">∣</mi><mi mathvariant="normal">绝</mi><mi mathvariant="normal">对</mi><mi mathvariant="normal">值</mi><mi mathvariant="normal">∣</mi><mo separator="true">,</mo><mi mathvariant="normal">然</mi><mi mathvariant="normal">后</mi><mi mathvariant="normal">夹</mi><mi mathvariant="normal">逼</mi></mrow><annotation encoding="application/x-tex">x^2y比x^2+y^2高阶,一般极限不存在,解法:加0\leq|绝对值|,然后夹逼</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.008548em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathdefault">x</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mord cjk_fallback">比</span><span class="mord"><span class="mord mathdefault">x</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.008548em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span><span class="mord cjk_fallback">高</span><span class="mord cjk_fallback">阶</span><span class="mord cjk_fallback">,</span><span class="mord cjk_fallback">一</span><span class="mord cjk_fallback">般</span><span class="mord cjk_fallback">极</span><span class="mord cjk_fallback">限</span><span class="mord cjk_fallback">不</span><span class="mord cjk_fallback">存</span><span class="mord cjk_fallback">在</span><span class="mord cjk_fallback">,</span><span class="mord cjk_fallback">解</span><span class="mord cjk_fallback">法</span><span class="mord cjk_fallback">:</span><span class="mord cjk_fallback">加</span><span class="mord">0</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">≤</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">∣</span><span class="mord cjk_fallback">绝</span><span class="mord cjk_fallback">对</span><span class="mord cjk_fallback">值</span><span class="mord">∣</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord cjk_fallback">然</span><span class="mord cjk_fallback">后</span><span class="mord cjk_fallback">夹</span><span class="mord cjk_fallback">逼</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="因为|\frac{x^2}{x^2+y^2}|\leq1,所以0\leq|\frac{x^2}{x^2+y^2}||y|\leq|y|" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\lim_{(x,y)\to(0,0)}\frac{xy^2}{x^2+y^4}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="在y=kx角度上,代入得\lim_{x\to0}\frac{k^2x}{1+k^4x^2}=0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="在x=y^2的角度上,代入得\lim_{x\to0}\frac{y^4}{y^4+y^4}=\frac12" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="两个极限不同,所以极限不存在" style=""><span></span><span></span></span>
连续
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\lim_{(x,y)\to(x_o,y_o)}f(x,y)=f(x_0,y_0)" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>lim</mi><mo></mo><mrow><mo>(</mo><mi>x</mi><mo separator="true">,</mo><mi>y</mi><mo>)</mo><mo>→</mo><mo>(</mo><msub><mi>x</mi><mi>o</mi></msub><mo separator="true">,</mo><msub><mi>y</mi><mi>o</mi></msub><mo>)</mo></mrow></msub><mi>f</mi><mo>(</mo><mi>x</mi><mo separator="true">,</mo><mi>y</mi><mo>)</mo><mo>=</mo><mi>f</mi><mo>(</mo><msub><mi>x</mi><mn>0</mn></msub><mo separator="true">,</mo><msub><mi>y</mi><mn>0</mn></msub><mo>)</mo></mrow><annotation encoding="application/x-tex">\lim_{(x,y)\to(x_o,y_o)}f(x,y)=f(x_0,y_0)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.1052em;vertical-align:-0.3551999999999999em;"></span><span class="mop"><span class="mop">lim</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.34480000000000005em;"><span style="top:-2.5198em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mopen mtight">(</span><span class="mord mathdefault mtight">x</span><span class="mpunct mtight">,</span><span class="mord mathdefault mtight" style="margin-right:0.03588em;">y</span><span class="mclose mtight">)</span><span class="mrel mtight">→</span><span class="mopen mtight">(</span><span class="mord mtight"><span class="mord mathdefault mtight">x</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.16454285714285719em;"><span style="top:-2.357em;margin-left:0em;margin-right:0.07142857142857144em;"><span class="pstrut" style="height:2.5em;"></span><span class="sizing reset-size3 size1 mtight"><span class="mord mathdefault mtight">o</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.143em;"><span></span></span></span></span></span></span><span class="mpunct mtight">,</span><span class="mord mtight"><span class="mord mathdefault mtight" style="margin-right:0.03588em;">y</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.16454285714285719em;"><span style="top:-2.357em;margin-left:-0.03588em;margin-right:0.07142857142857144em;"><span class="pstrut" style="height:2.5em;"></span><span class="sizing reset-size3 size1 mtight"><span class="mord mathdefault mtight">o</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.143em;"><span></span></span></span></span></span></span><span class="mclose mtight">)</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.3551999999999999em;"><span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord"><span class="mord mathdefault">x</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">0</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord"><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.30110799999999993em;"><span style="top:-2.5500000000000003em;margin-left:-0.03588em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">0</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mclose">)</span></span></span></span></span><span></span></span>
偏导数
<span class="equation-text" contenteditable="false" data-index="0" data-equation="f'_x(x_o,y_o)=\lim_{\triangle x\to0}\frac{f(x_o+\triangle x,y_o)-f(x_o,y_o)}{\triangle x}=\frac{d}{dx}f(x,y_o)|_{x=x_o}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="先代后求:求导前可对不导的自变量先代值\\ f(x,1)=0 \to f'_x(x,1)=0"><span></span><span></span></span>
全微分
偏导数和全微分的计算
题型
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P164 例5,例6" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>P</mi><mn>164</mn><mi mathvariant="normal">例</mi><mn>5</mn><mi mathvariant="normal">,</mi><mi mathvariant="normal">例</mi><mn>6</mn></mrow><annotation encoding="application/x-tex"></annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="mord"></span></span></span></span></span><span></span></span><span class="equation-text" contenteditable="false" data-index="1" data-equation="(xy-yf(x))dx+(f(x)+y^2)dy=du(x,y),f(x)有一阶连续导数" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mo>(</mo><mi>x</mi><mi>y</mi><mo>−</mo><mi>y</mi><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>)</mo><mi>d</mi><mi>x</mi><mo>+</mo><mo>(</mo><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>+</mo><msup><mi>y</mi><mn>2</mn></msup><mo>)</mo><mi>d</mi><mi>y</mi><mo>=</mo><mi>d</mi><mi>u</mi><mo>(</mo><mi>x</mi><mo separator="true">,</mo><mi>y</mi><mo>)</mo><mi mathvariant="normal">,</mi><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mi mathvariant="normal">有</mi><mi mathvariant="normal">一</mi><mi mathvariant="normal">阶</mi><mi mathvariant="normal">连</mi><mi mathvariant="normal">续</mi><mi mathvariant="normal">导</mi><mi mathvariant="normal">数</mi></mrow><annotation encoding="application/x-tex">(xy-yf(x))dx+(f(x)+y^2)dy=du(x,y),f(x)有一阶连续导数</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">−</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mclose">)</span><span class="mclose">)</span><span class="mord mathdefault">d</span><span class="mord mathdefault">x</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.064108em;vertical-align:-0.25em;"></span><span class="mord"><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span><span class="mclose">)</span><span class="mord mathdefault">d</span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathdefault">d</span><span class="mord mathdefault">u</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mclose">)</span><span class="mord cjk_fallback">,</span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mclose">)</span><span class="mord cjk_fallback">有</span><span class="mord cjk_fallback">一</span><span class="mord cjk_fallback">阶</span><span class="mord cjk_fallback">连</span><span class="mord cjk_fallback">续</span><span class="mord cjk_fallback">导</span><span class="mord cjk_fallback">数</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="有题设可知,\frac{\partial u}{\partial x}=xy-yf(x),\frac{\partial u}{\partial x}=f(x)+y^2" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">有</mi><mi mathvariant="normal">题</mi><mi mathvariant="normal">设</mi><mi mathvariant="normal">可</mi><mi mathvariant="normal">知</mi><mi mathvariant="normal">,</mi><mfrac><mrow><mi mathvariant="normal">∂</mi><mi>u</mi></mrow><mrow><mi mathvariant="normal">∂</mi><mi>x</mi></mrow></mfrac><mo>=</mo><mi>x</mi><mi>y</mi><mo>−</mo><mi>y</mi><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo separator="true">,</mo><mfrac><mrow><mi mathvariant="normal">∂</mi><mi>u</mi></mrow><mrow><mi mathvariant="normal">∂</mi><mi>x</mi></mrow></mfrac><mo>=</mo><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>+</mo><msup><mi>y</mi><mn>2</mn></msup></mrow><annotation encoding="application/x-tex">有题设可知,\frac{\partial u}{\partial x}=xy-yf(x),\frac{\partial u}{\partial x}=f(x)+y^2</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.2251079999999999em;vertical-align:-0.345em;"></span><span class="mord cjk_fallback">有</span><span class="mord cjk_fallback">题</span><span class="mord cjk_fallback">设</span><span class="mord cjk_fallback">可</span><span class="mord cjk_fallback">知</span><span class="mord cjk_fallback">,</span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8801079999999999em;"><span style="top:-2.6550000000000002em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight" style="margin-right:0.05556em;">∂</span><span class="mord mathdefault mtight">x</span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.394em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight" style="margin-right:0.05556em;">∂</span><span class="mord mathdefault mtight">u</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.7777700000000001em;vertical-align:-0.19444em;"></span><span class="mord mathdefault">x</span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">−</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.2251079999999999em;vertical-align:-0.345em;"></span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mclose">)</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.16666666666666666em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8801079999999999em;"><span style="top:-2.6550000000000002em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight" style="margin-right:0.05556em;">∂</span><span class="mord mathdefault mtight">x</span></span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.394em;"><span class="pstrut" style="height:3em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight" style="margin-right:0.05556em;">∂</span><span class="mord mathdefault mtight">u</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.008548em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span></span></span></span></span></span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="对第一个等式进行y偏导,对第二个等式进行x偏导,可得x-f(x)和f'(x)" style=""><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">对</mi><mi mathvariant="normal">第</mi><mi mathvariant="normal">一</mi><mi mathvariant="normal">个</mi><mi mathvariant="normal">等</mi><mi mathvariant="normal">式</mi><mi mathvariant="normal">进</mi><mi mathvariant="normal">行</mi><mi>y</mi><mi mathvariant="normal">偏</mi><mi mathvariant="normal">导</mi><mi mathvariant="normal">,</mi><mi mathvariant="normal">对</mi><mi mathvariant="normal">第</mi><mi mathvariant="normal">二</mi><mi mathvariant="normal">个</mi><mi mathvariant="normal">等</mi><mi mathvariant="normal">式</mi><mi mathvariant="normal">进</mi><mi mathvariant="normal">行</mi><mi>x</mi><mi mathvariant="normal">偏</mi><mi mathvariant="normal">导</mi><mi mathvariant="normal">,</mi><mi mathvariant="normal">可</mi><mi mathvariant="normal">得</mi><mi>x</mi><mo>−</mo><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mi mathvariant="normal">和</mi><msup><mi>f</mi><mo mathvariant="normal">′</mo></msup><mo>(</mo><mi>x</mi><mo>)</mo></mrow><annotation encoding="application/x-tex">对第一个等式进行y偏导,对第二个等式进行x偏导,可得x-f(x)和f'(x)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7777700000000001em;vertical-align:-0.19444em;"></span><span class="mord cjk_fallback">对</span><span class="mord cjk_fallback">第</span><span class="mord cjk_fallback">一</span><span class="mord cjk_fallback">个</span><span class="mord cjk_fallback">等</span><span class="mord cjk_fallback">式</span><span class="mord cjk_fallback">进</span><span class="mord cjk_fallback">行</span><span class="mord mathdefault" style="margin-right:0.03588em;">y</span><span class="mord cjk_fallback">偏</span><span class="mord cjk_fallback">导</span><span class="mord cjk_fallback">,</span><span class="mord cjk_fallback">对</span><span class="mord cjk_fallback">第</span><span class="mord cjk_fallback">二</span><span class="mord cjk_fallback">个</span><span class="mord cjk_fallback">等</span><span class="mord cjk_fallback">式</span><span class="mord cjk_fallback">进</span><span class="mord cjk_fallback">行</span><span class="mord mathdefault">x</span><span class="mord cjk_fallback">偏</span><span class="mord cjk_fallback">导</span><span class="mord cjk_fallback">,</span><span class="mord cjk_fallback">可</span><span class="mord cjk_fallback">得</span><span class="mord mathdefault">x</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">−</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.001892em;vertical-align:-0.25em;"></span><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mclose">)</span><span class="mord cjk_fallback">和</span><span class="mord"><span class="mord mathdefault" style="margin-right:0.10764em;">f</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.751892em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">′</span></span></span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord mathdefault">x</span><span class="mclose">)</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="因为f(x)一阶连续导数,所以\frac{\partial^2 u}{\partial x\partial y}=\frac{\partial^2 u}{\partial y\partial x},即x-f(x)=f'(x)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P165例1,微分形式不变" style=""><span></span><span></span></span>
极值与最值
无条件极值
条件极值
计算时,如果函数具有轮换对称性,可以用x=y=z直接求解。
题型
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P175 例3(无条件极值)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="由方程x^2+y^2+z^2-2x+2y-4z-10=0所确定函数z=z(x,y)的极值" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="隐函数要求出所有变量x,y,z的值,然后再用充分条件验证"><span></span><span></span></span>
二重积分
性质
<span class="equation-text" contenteditable="false" data-index="0" data-equation="若在D上f(x,y)\leq g(x,y),则\iint f(x,y)d\sigma\leq\iint g(x,y)d\sigma" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="mS\leq\iint f(x,y)d\sigma\leq MS" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="|\iint f(x,y)d\sigma|\leq\iint |f(x,y)|d\sigma" style=""><span></span><span></span></span>
积分中值定理
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\iint f(x,y)d\sigma=f(\xi,\eta)S" style=""><span></span><span></span></span>
题型
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P187页 例4" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="先看D是否存在对称性,能否做辅助线" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="看函数能否拆分,利用奇偶性简化" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="看函数是否为f(\sqrt{x^2+y^2})、f(\frac yx)、f(\frac xy),进行极坐标变换" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P194 例2(二重定积分,可看作常数)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="综合题,要多看 "><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P195 例3(二重变积分,用求导方式)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="P197 例3(二重积分不等式)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int_a^bf(x)dx\int_a^b\frac1{f(x)}dx\geq (b-a)^2" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="遇到定积分相乘时,可以考虑用二重积分或者柯西不等式证明" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\int_a^bf(x)dx\int_a^b\frac1{f(x)}dx=\int_a^bf(x)dx\int_a^b\frac1{f(y)}dy=\iint_a^b\frac{f(x)}{f(y)}dxdy" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="柯西不等式" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="参数方程求二重积分" style=""><span></span><span></span></span>
常识
<span class="equation-text" contenteditable="false" data-index="0" data-equation="椭圆方程:\frac{x^2}{a^2}+\frac{y^2}{b^2}=1,S=\pi ab(a、b是半轴!)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="圆锥体积=\frac13圆柱体积=\frac{\pi}3r^2h"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="球体体积=\frac{4}{3}\pi r^3,球体表面积=4\pi r^2" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="三角形"><span><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">三</mi><mi mathvariant="normal">角</mi><mi mathvariant="normal">形</mi></mrow><annotation encoding="application/x-tex">三角形</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0em;vertical-align:0em;"></span><span class="mord cjk_fallback">三</span><span class="mord cjk_fallback">角</span><span class="mord cjk_fallback">形</span></span></span></span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="海伦公式S=\sqrt{p(p-a)(p-b)(p-c)}(p为半周长\frac{a+b+c}{2},a,b,c为三条边)" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="定积分、二重积分、导数都是一个常数" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="函数移动:左加右减"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="双纽线:(x^2+y^2)^2=x^2-y^2" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="C_n^m=\frac{A_n^m}{A_m^m}=\frac{n!}{m!n-m!}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="A是B的充分条件:A\to B" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\bar{x}=\frac{\int_0^1x\rho (x)dx}{\int_0^1\rho(x)dx}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="2x^3-x^2-1=0,可以通过观察法,先看出x=1是其中一个解,然后化成(x-1)(...),用长除法算出" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="I_1、I_2和I_3比大小,作差法" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="倍角公式" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\sin{2x}=2\sin{x}\cos{x}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\cos{2x}=\cos^2x-\sin^2x=1-2\sin^2x=2\cos^2x-1" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\tan{2x}=\frac{2\tan x}{1-\tan^2x}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="rdrd\theta = dxdy" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="广义洛必达:\frac{\infty}{\infty},只要分母趋于无穷就可以直接洛必达"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="外函数连续,内函数有极限:\lim_{n\to\infty}\arctan{x_n}=\arctan{(\lim_{n\to\infty}x_n)}" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="n次多项式,f^n(x)\neq0,则最多有n个实根(罗尔原话),即最多n-1有f'(x)=0,也就是n-1个水平切线" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\lim_{x\to 0}\frac{f(x)-1}{x^2}=\lim_{x\to 0}\frac{f'(x)}{2x}=\lim_{x\to 0}\frac{f''(x)}{2}=1" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\lim_{x\to 0}\frac{f(x)-1}{x^2}=\lim_{x\to 0}\frac{f(0)+f'(0)x+\frac{f''(0)}{2}x^2+0(x^2)-1}{x^2}=1\to f(0)=1,f''(0)=2" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="积分时,\int f()内部复杂,考虑还元,如f(x+y),用u=x+y换元" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="r=1+\cos \theta 与 \theta = 0,\theta = \frac{\pi}{2}围成的图形绕极轴旋转一周所得旋转体的体积为" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="证明部分式子是否大于小于0时,可以将部分式子设为f(x),然后求导判断单调区间" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="\frac{xe^x+e^x+1}{e^x}>0,判断这个式子,只需要设f(x)=xe^x+e^x+1,然后判断f'(x)的单调区间就行" style=""><span></span><span></span></span>
线代
当A不满秩(行列式为0)时,0为A的特征值
<span class="equation-text" contenteditable="false" data-index="0" data-equation="列向量\alpha和\beta \to r(\alpha \beta^T)=1" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="求通解000!!!"><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="看到A^*,想到r(A)和r(A^*)的关系" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="r(A)=n,r(A^*)=n" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="r(A)=n-1,r(A^*)=1" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="r(A)<n-1,r(A^*)=0\to AA^*=0\to A^*的每一列都是Ax=0的解" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="如AB=0,则" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="B的列向量是Ax=0的解,即|A|=0" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="r(A) + r(B) <= n" style=""><span></span><span></span></span>
<span class="equation-text" contenteditable="false" data-index="0" data-equation="A合同于B,A和B必须都是实对称" style=""><span></span><span></span></span>
好题!判断相似和合同
李四第一套22题
求Ax=b时,注意求通解和特解,不要直接就把自由变量代入1,然后对b求解。
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