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修改assert文件夹名称, 修正图片链接
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Cyletix committed Jan 27, 2025
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4 changes: 2 additions & 2 deletions Other/例题/高数1真题/数一2010.md
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Expand Up @@ -227,7 +227,7 @@
已知曲线 $L$ 的方程为 $y=1-|x|(x \in[-1,1])$, 起点是 $(-1,0)$, 终点为 $(1,0)$, 则曲线积分 $\displaystyle \int_{L} x y \mathrm{~d} x+x^{2} \mathrm{~d} y=$
### (11)
答 应填 0 .
- <br>![|200](/_assert_/Images/20241214204806.png)
- <br>![|200](/_assets_/Images/20241214204806.png)
- $\displaystyle \begin{aligned} & \int_L x y \mathrm{~d} x+x^2 \mathrm{~d} y= \end{aligned}$
- $\displaystyle \begin{aligned}\xlongequal[]{照抄}\int_{L+L^{\prime}} x y \mathrm{~d} x+x^2 \mathrm{~d} y-\int_{L^{\prime}} x y \mathrm{~d} x+x^2 \mathrm{~d} y\end{aligned}$
- $\begin{aligned}\underbrace{\oint_{L+L'} x y d x+x^2 d y}_{P=x y \quad Q=x^2}\xlongequal[逆时针,加负号]{\frac{\partial Q}{\partial z}-\frac{\partial P}{\partial y}=}-\iint_D(2 x-x) d x d y\end{aligned}$
Expand All @@ -238,7 +238,7 @@
## (12)
设 $\Omega=\left\{(x, y, z) \mid x^{2}+y^{2} \leqslant z \leqslant 1\right\}$, 则 $\Omega$ 的形心的坚坐标 $\bar{z}=$
### (12)
- <br>![|150](/_assert_/Images/20241214085245.png)
- <br>![|150](/_assets_/Images/20241214085245.png)
-


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10 changes: 5 additions & 5 deletions Other/例题/高数1真题/数一2011.md
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Expand Up @@ -12,7 +12,7 @@
- (2)拐点与极值点 : 对于多项式函数或存在任意阶导数的函数 $f(x)$ ,设点 $\left(x_0, f\left(x_0\right)\right)$ 为曲线 $y=f(x)$ 上一点,则有如下结论:
- (a) 若 $x_0$ 是 $f(x)$ 的极值点,则点 $\left(x_0, f\left(x_0\right)\right)$ 一定不是曲线 $y=f(x)$ 的拐点.
- (b) 若点 $\left(x_0, f\left(x_0\right)\right)$ 是曲线 $y=f(x)$ 的拐点,则 $x_0$ 也一定不是 $f(x)$ 的极值点.
- 穿针引线怯:设多项式的最高次项系数大于零.从数轴上最右边的根的右上方开始穿根,<br>根据零点的重数的奇偶性决定穿或者不穿,即奇穿偶不穿,或奇穿偶回。<br>![|200](/_assert_/Images/20241213084834.png)
- 穿针引线怯:设多项式的最高次项系数大于零.从数轴上最右边的根的右上方开始穿根,<br>根据零点的重数的奇偶性决定穿或者不穿,即奇穿偶不穿,或奇穿偶回。<br>![|200](/_assets_/Images/20241213084834.png)
- 因为 $x=3$ 是方程 $y=(x-1)(x-2)^2(x-3)^3(x-4)^4=0$ 的 3 重根
- 所以它是方程 $y^{\prime \prime}=0$ 的 单根, 从而函数 $y=(x-1)(x-2)^2(x-3)^3(x-4)^4$ 的二阶导数在点 $x=3$ 的两侧附近改变正负号,
- 故点 $(3,0)$ 是曲线 $y=(x-1)(x-2)^2(x-3)^3(x-4)^4$ 的拐点.
Expand Down Expand Up @@ -162,7 +162,7 @@
- 由 $y(0)=0$, 得 $C=0$,
- 所以 $y=\mathrm{e}^{-x} \sin x$.
$\qquad$
- <br>![|600](/_assert_/Images/20241214110129.png)
- <br>![|600](/_assets_/Images/20241214110129.png)
- 2012 年数二试题<br>微分方程 $y \mathrm{~d} x+\left(x-3 y^2\right) \mathrm{d} y=0$ 满足条件 $\left.y\right|_{x=1}=1$的解为 $y=$
## (11)
设函数 $F(x, y)=\int_{0}^{x y} \frac{\sin t}{1+t^{2}} \mathrm{~d} t$, 则 $\left.\frac{\partial^{2} F}{\partial x^{2}}\right|_{\substack{x=0 \\ y=2}}=$
Expand All @@ -181,14 +181,14 @@
## (12)
设 $L$ 是柱面 $x^{2}+y^{2}=1$ 与平面 $z=x+y$ 的交线, 从 $z$ 轴正向往 $z$ 轴负向看去为逆时针方向, 则曲线积分 $\oint_{L} x z \mathrm{~d} x+x \mathrm{~d} y+\frac{y^{2}}{2} \mathrm{~d} z=$
### (12)
- <br>![|100](/_assert_/Images/20241214212344.png)![|120](/_assert_/Images/20241214215516.png)
- <br>![|100](/_assets_/Images/20241214212344.png)![|120](/_assets_/Images/20241214215516.png)
- 解题过程 如图所示,平面 $\Sigma$ 取为平面 $x+y-z=0$ 上被 $L$ 截得的有限部分. 根据右手规则, $\boldsymbol{\Sigma}$ 的法向量取为 $\xrightarrow[]{z朝上,是正数}\boldsymbol{n}=(-1,-1,1)$ ,单位法向量为 $\left(-\frac{1}{\sqrt{3}},-\frac{1}{\sqrt{3}}, \frac{1}{\sqrt{3}}\right)$.
- $\begin{aligned} & \oint_L x z \mathrm{~d} x+x \mathrm{~d} y+\frac{y^2}{2} \mathrm{~d} z=\iint_{\Sigma}\left|\begin{array}{ccc}-\frac{1}{\sqrt{3}} & -\frac{1}{\sqrt{3}} & \frac{1}{\sqrt{3}} \\\frac{\partial}{\partial x} & \frac{\partial}{\partial y} & \frac{\partial}{\partial z} \\x z & x & \frac{y^2}{2}\end{array}\right| \mathrm{d} S \end{aligned}$
- $\xlongequal[注意a12是负号]{按第一行展开}-\frac{\sqrt{3}}{3} y+(-1) \cdot\left(-\frac{\sqrt{3}}{3}\right)(-x)+\frac{\sqrt{3}}{3}$
- $\begin{aligned} =\frac{1}{\sqrt{3}} \iint_{\mathbf{Z}}(1-\mathbf{x}-\mathbf{y}) \mathrm{dS} \xrightarrow[]{之后全部投影到dxdy}\end{aligned}$
- $\begin{aligned} d S & =\sqrt{1+(-1)^2+(-1)^2} d xd y=\sqrt{3} d x d y\end{aligned}$
- $\begin{aligned} & =\frac{1}{\sqrt{3}} \iint_D(1-x-y) \cdot \sqrt{3} d x d y \end{aligned}$
- $\begin{aligned} =\iint_D(1-x-y) d x d y \end{aligned}$<br>![|50](/_assert_/Images/20241214215924.png)
- $\begin{aligned} =\iint_D(1-x-y) d x d y \end{aligned}$<br>![|50](/_assets_/Images/20241214215924.png)
- $\begin{aligned} =\iint_D1d x d y \end{aligned}$
- $\begin{aligned}\xlongequal[直接算面积,半径为1]{被积函数是常数} \pi\end{aligned}$
## (13)
Expand Down Expand Up @@ -230,7 +230,7 @@
(本题满分 9 分) 设函数 $z=f(x y, y g(x))$, 其中函数 $f$ 具有二阶连续偏导数, 函数 $g(x)$ 可导, 且在 $x=1$ 处取 得极值 $g(1)=1$. 求 $\left.\frac{\partial^{2} z}{\partial x \partial y}\right|_{\substack{x=1 \\ y=1}}$.
### (16)
- 该问题涉及求函数 $z = f(xy, yg(x))$ 在点 $(x=1, y=1)$ 的二阶混合偏导数 $\frac{\partial^{2} z}{\partial x \partial y}$
- 因为是求具体点的值,可以利用先代后求<br>![|200](/_assert_/Images/20241213122231.png)
- 因为是求具体点的值,可以利用先代后求<br>![|200](/_assets_/Images/20241213122231.png)
- 计算函数 $z = f(xy, yg(x))$ 对x的一阶偏导数 $\frac{\partial z}{\partial x}$。
- 使用链式法则得:$\frac{\partial z}{\partial x} = y f_1^{\prime} + y g^{\prime}(x) f_2^{\prime}$。
- 先带后求得,计算 $\left.\frac{\partial z}{\partial x}\right|_{x=1}$。
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6 changes: 3 additions & 3 deletions Other/例题/高数1真题/数一2012.md
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Expand Up @@ -169,7 +169,7 @@
- 计算 $P\{X < Y\}$
- 求 $X < Y$ 的概率相当于在 $x < y$ 的区域内对联合概率密度函数进行积分
- 小x的范围就是大X的范围
- 之后只关注$Y=g(X)$,画图,一图三吃![image|300](/_assert_/Images/IMG_5760.jpeg)
- 之后只关注$Y=g(X)$,画图,一图三吃![image|300](/_assets_/Images/IMG_5760.jpeg)
- 计算过程:
- $P\{X < Y\} = \iint_{x < y} f(x, y) dx dy\xlongequal[]{固定,可变}\int_0^{+\infty} d y \int_0^y 4 e^{-x-4 y} d x$
- $\xlongequal[]{分离常数}4 \int_0^{+\infty} e^{-4 y} d y \int_0^y e^{-x} d x=\frac{1}{5}$
Expand Down Expand Up @@ -260,7 +260,7 @@
### (12)
答 应填 $\frac{\sqrt{3}}{12}$.
- 转换投影是==对积分区域转换投影==,还是==对被积函数转换投影==?
- <br>![|200](/_assert_/Images/20241214222033.png),积分区域投影后,![|150](/_assert_/Images/20241214222112.png)
- <br>![|200](/_assets_/Images/20241214222033.png),积分区域投影后,![|150](/_assets_/Images/20241214222112.png)
- 要投影的方程:$z=1-x-y$
- 解 记 $D=\{(x, y) \mid x+y \leqslant 1, x \geqslant 0, y \geqslant 0\}$, 则
- $\begin{aligned}\iint_{\Sigma} y^{2} \mathrm{~d} S=\end{aligned}$
Expand Down Expand Up @@ -474,7 +474,7 @@
- 本题主要考查第二类曲线积分的计算. 可以补线段成为一个闭曲线后再利用格林公式.
- ==格林公式== <br>设闭区域 $D$ 由分段光滑的曲线 $L$ 围成, 若函数 $P(x, y)$ 及 $Q(x, y)$ 在 $D$ 上具有一阶连续偏导数, 则有<br>$\begin{aligned}\oint_L P \mathrm{~d} x+Q \mathrm{~d} y=\iint_D\left(\frac{\partial Q}{\partial x}-\frac{\partial P}{\partial y}\right) \mathrm{d} x \mathrm{~d} y\end{aligned}$
- 其中 $L$ 是 $D$ 的取正向的边界曲线. <br>(一定要注意 $L$ 的方向, 若方向相反, 则多一个负号. )
- <br>![|150](/_assert_/Images/20241214202710.png),补线后![|150](/_assert_/Images/20241214203025.png)
- <br>![|150](/_assets_/Images/20241214202710.png),补线后![|150](/_assets_/Images/20241214203025.png)

- $\begin{aligned}\iint_D\left(\frac{\partial Q}{\partial x}-\frac{\partial P}{\partial y}\right) \mathrm{d} x \mathrm{~d} y=3 x^2+1-3 x^2=1\end{aligned}$
- 则补条线再用格林
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4 changes: 2 additions & 2 deletions Other/例题/高数1真题/数一2013.md
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Expand Up @@ -363,7 +363,7 @@
- ++-,因此是双叶双曲面

#### 第二问
- <br>![|150](/_assert_/Images/20241214092608.png),AB绕z轴旋转一周![|200](/_assert_/Images/20241214092458.png)
- <br>![|150](/_assets_/Images/20241214092608.png),AB绕z轴旋转一周![|200](/_assets_/Images/20241214092458.png)
- (II) 设 $\Omega$ 的形心坐标为 $(\bar{x}, \bar{y}, \bar{z})$.
- 由曲面 $\Sigma$ 的方程知, $\Omega$ 关于 $x O z, y O z$面对称,从而x和y的坐标有了
- $\begin{aligned}\bar{x}=\frac{\iiint_{\Omega} x \mathrm{~d} x \mathrm{~d} y \mathrm{~d} z}{\iiint_{\Omega} \mathrm{d} x \mathrm{~d} y \mathrm{~d} z}=0,\end{aligned}$
Expand Down Expand Up @@ -448,7 +448,7 @@
- 秒杀01
- 根据Y的范围求出X的范围
- 确定积分限的范围
- 画图![image|200](/_assert_/Images/2023.12.19-23.54.png))
- 画图![image|200](/_assets_/Images/2023.12.19-23.54.png))
- 写出$Y$ 的分布函数 $F_Y(y)=P(Y ≤ y)$
- 分段讨论
- 当 $y < 1$ 时
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18 changes: 9 additions & 9 deletions Other/例题/高数1真题/数一2014.md
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Expand Up @@ -66,8 +66,8 @@
- [07:48](file:///C:/Users/wangpanfeng/Videos/01.%E6%95%B0%E5%AD%A6%E4%B8%80/01.2014%E5%B9%B4%E6%95%B0%E4%B8%80%E7%9C%9F%E9%A2%98/01.2014%E5%B9%B4%E8%80%83%E7%A0%94%E6%95%B0%E5%AD%A6%E7%9C%9F%E9%A2%98%E9%80%89%E6%8B%A9%E9%A2%98%EF%BC%88%E6%95%B0%E4%B8%80%EF%BC%89.mp4#t=07:48)
答 应选(D).
- 题中问的是,
- 当$f^{\prime}(x) \geqslant 0$时,fx和gx的一个大小关系<br>![|150](/_assert_/Images/20241213075730.png)
- 当$f^{\prime \prime}(x) \geqslant 0$时,fx与gx的大小关系<br>![|150](/_assert_/Images/20241213075847.png)
- 当$f^{\prime}(x) \geqslant 0$时,fx和gx的一个大小关系<br>![|150](/_assets_/Images/20241213075730.png)
- 当$f^{\prime \prime}(x) \geqslant 0$时,fx与gx的大小关系<br>![|150](/_assets_/Images/20241213075847.png)

## (3)
设 $f(x, y)$ 是连续函数, 则 $\int_{0}^{1} \mathrm{~d} y \int_{-\sqrt{1-y^{2}}}^{1-y} f(x, y) \mathrm{d} x=(\quad)$
Expand All @@ -79,11 +79,11 @@
### (3)
- [12:36](file:///C:/Users/wangpanfeng/Videos/01.%E6%95%B0%E5%AD%A6%E4%B8%80/01.2014%E5%B9%B4%E6%95%B0%E4%B8%80%E7%9C%9F%E9%A2%98/01.2014%E5%B9%B4%E8%80%83%E7%A0%94%E6%95%B0%E5%AD%A6%E7%9C%9F%E9%A2%98%E9%80%89%E6%8B%A9%E9%A2%98%EF%BC%88%E6%95%B0%E4%B8%80%EF%BC%89.mp4#t=12:36)
答 应选(D).
- AB选项是交换x和y的积分次序<br>![|200](/_assert_/Images/20241213083458.png)
- AB选项是交换x和y的积分次序<br>![|200](/_assets_/Images/20241213083458.png)
- $\begin{array}{ll}-1 \leqslant x \leqslant 0, & 0 \leqslant y \leqslant \sqrt{1-x^2}\end{array}$
- $0 \leqslant x \leqslant 1, 0 \leqslant y \leqslant 1-x$
- 在直角坐标系下,原式 $=\int_{-1}^0 \mathrm{~d} x \int_0^{\sqrt{1-x}} f(x, y) \mathrm{d} y+\int_0^1 \mathrm{~d} x \int_0^{1-x} f(x, y) \mathrm{d} y$
- CD选项是将直角坐标系化为极坐标系<br>![|200](/_assert_/Images/20241213083837.png)
- CD选项是将直角坐标系化为极坐标系<br>![|200](/_assets_/Images/20241213083837.png)
- 在极坐标系下,<br>原式 $=\int_0^{\frac{\pi}{2}} \mathrm{~d} \theta \int_0^{\frac{1}{\cos \theta+\sin \theta}} f(r \cos \theta, r \sin \theta) r \mathrm{~d} r+\int_{\frac{\pi}{2}}^\pi d \theta \int_0^1 f(r \cos \theta, r \sin \theta) r \mathrm{~d} r$
- 故应该选(D).

Expand Down Expand Up @@ -243,7 +243,7 @@
### (12)
- [09:25](file:///C:/Users/wangpanfeng/Videos/01.%E6%95%B0%E5%AD%A6%E4%B8%80/01.2014%E5%B9%B4%E6%95%B0%E4%B8%80%E7%9C%9F%E9%A2%98/02.2014%E5%B9%B4%E8%80%83%E7%A0%94%E6%95%B0%E5%AD%A6%E7%9C%9F%E9%A2%98%E5%A1%AB%E7%A9%BA%E9%A2%98%EF%BC%88%E6%95%B0%E4%B8%80%EF%BC%89.mp4#t=09:25)
答 应填 $\pi$.
- <br>![|150](/_assert_/Images/20241214220956.png)
- <br>![|150](/_assets_/Images/20241214220956.png)
- 斯托克斯如何判断法向量
- 右手螺旋准则,==如果右手大拇指是朝上的z就为+1,如果是朝下的z就为-1==
- 设平面 $\Sigma: y+z=0$, 取上侧, 其法向量为 $n=(0,1,1)$, 故单位法向量为 $\boldsymbol{n}^{\circ}=\left(0, \frac{1}{\sqrt{2}}, \frac{1}{\sqrt{2}}\right)$.
Expand Down Expand Up @@ -339,7 +339,7 @@
(本题满分 10 分)设 $\Sigma$ 为曲面 $z=x^{2}+y^{2}(z \leqslant 1)$ 的上侧, 计算曲面积分$I=\iint_{\Sigma}(x-1)^{3} \mathrm{~d} y \mathrm{~d} z+(y-1)^{3} \mathrm{~d} z \mathrm{~d} x+(z-1) \mathrm{d} x \mathrm{~d} y .$
#### (18)
- [21:51](file:///C:/Users/wangpanfeng/Videos/01.%E6%95%B0%E5%AD%A6%E4%B8%80/01.2014%E5%B9%B4%E6%95%B0%E4%B8%80%E7%9C%9F%E9%A2%98/03.2014%E5%B9%B4%E8%80%83%E7%A0%94%E6%95%B0%E5%AD%A6%E7%9C%9F%E9%A2%98%E8%A7%A3%E7%AD%94%E9%A2%981%EF%BC%88%E6%95%B0%E4%B8%80%EF%BC%89%EF%BC%8815~18%E9%A2%98%EF%BC%89.mp4#t=21:51)
- <br>![|150](/_assert_/Images/20241214234736.png)![|200](/_assert_/Images/20241214235335.png)
- <br>![|150](/_assets_/Images/20241214234736.png)![|200](/_assets_/Images/20241214235335.png)
#### 转换投影法
- $\begin{aligned} D: \left\{(x, y) \mid x^{2} + y^{2} \leq 1\right\}\end{aligned}$
- $\begin{aligned} I = \iint_{D} (-Pzx - Qzy + R) \, dx \, dy \end{aligned}$
Expand All @@ -355,7 +355,7 @@
- $\begin{aligned}I=-20 \cdot \frac{\pi}{8}-8 \cdot \frac{\pi}{16}-\pi=-\frac{5}{2} \pi-\frac{\pi}{2}-\pi=-4 \pi\end{aligned}$

#### 高斯
- <br>![|200](/_assert_/Images/20241215001311.png)
- <br>![|200](/_assets_/Images/20241215001311.png)
- $\begin{aligned} \Sigma_1: \left\{(x, y, z) \mid x^2 + y^2 \leq 1, \, z = 1\right\}, \, \text{向下}, \end{aligned}$
- 负方向的高斯,结果外面要加负号
- $\begin{aligned} \Omega_1 = \Sigma_1 \text{和} \Sigma \text{所围区域}. \end{aligned}$
Expand All @@ -364,7 +364,7 @@
- $\begin{aligned} = -\iiint_{\Omega} \left[3(x-1)^2 + 3(y-1)^2 + 1\right] \, dV \end{aligned}$
- $\begin{aligned}\xlongequal[]{去括号}-\iiint_{\Omega}\left[3 x^2-6 x+3+3 y^2-6 y+3+1\right] d V\end{aligned}$
- $\begin{aligned}=-\iiint_{\Omega}\left[3\left(x^2+y^2\right)+7\right] d V\xrightarrow[截面法算]{柱线法算}\end{aligned}$
- <br>![|150](/_assert_/Images/20241215001838.png)
- <br>![|150](/_assets_/Images/20241215001838.png)
- $\begin{aligned} & =-\int_0^1 d z \iint_{D_z}\left[3\left(x^2+y^2\right)+7\right] d x d y \end{aligned}$
- $\begin{aligned} =-\int_0^1 d z \int_0^{2 \pi} d \theta \int_0^{\sqrt{z}}\underbrace{\left(3 r^2+7\right) r}_{\left(3 r^3+7 \tau\right)}d r \xrightarrow[]{\frac{3}{4} r^4+\left.\frac{7}{2} r^2\right|_0 ^{\sqrt{z}}=\frac{3}{4} z^2+\frac{7}{2} z}\end{aligned}$
- $=-\int_0^1\left(\frac{3}{2} \pi z^2+7 \pi z\right) d z=-4 \pi$.
Expand Down Expand Up @@ -402,7 +402,7 @@
- 概率密度$f(x)=\left\{\begin{array}{cl}\frac{1}{b-a}, & a<x<b \\ 0, & \text { 其他 }\end{array}\right.$
- 当 $X=1$ 时,概率密度 $f_{Y \mid X}(y \mid 1)=\left\{\begin{array}{ll}1, & 0<y<1, \\ 0, & \text { 其他. }\end{array}\right.$
- $X=2$ 时,概率密度 $f_{Y \mid X}(y \mid 2)=\left\{\begin{array}{ll}\frac{1}{2}, & 0<y<2, \\ 0, & \text { 其他. }\end{array}\right.$
- 画图![image|250](/_assert_/Images/https://obsidian-picture-1314838930.cos.ap-beijing.myqcloud.com/2023.12.20-13.05.png)
- 画图![image|250](/_assets_/Images/https://obsidian-picture-1314838930.cos.ap-beijing.myqcloud.com/2023.12.20-13.05.png)
- 一图三吃:吃01,吃转化,吃吃积分限
- 根据 $y$ 的不同取值
- 当 $y < 0$,$F_Y(y) = 0$
Expand Down
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