Featured image of post 考研常用公式與範例

考研常用公式與範例

十年不見了,微積分

微分常用公式

  1. $$(f(x) + g(x))' = f'(x) + g'(x)$$

  2. $$(f(x) - g(x))' = f'(x) - g'(x)$$

  3. $$(cf(x))' = c f'(x) \quad \text{(c為常數)}$$

  4. $$(f(x)g(x))' = f'(x)g(x) + f(x)g'(x) \quad \text{(乘法法則)}$$

  5. $$\left(\frac{f(x)}{g(x)}\right)' = \frac{f'(x)g(x) - f(x)g'(x)}{[g(x)]^2} \quad \text{(除法法則)}$$

  6. $$(f(g(x)))' = f'(g(x)) \cdot g'(x) \quad \text{(鏈式法則)}$$

image-20250427071506366

  1. $$\frac{d}{dx}(x^n) = nx^{n-1}$$

  2. $$\frac{d}{dx}(\sin x) = \cos x$$

  3. $$\frac{d}{dx}(\cos x) = -\sin x$$

  4. $$\frac{d}{dx}(\tan x) = \sec^2 x$$

  5. $$\frac{d}{dx}(e^x) = e^x$$

  6. $$\frac{d}{dx}(\ln x) = \frac{1}{x}$$

積分常用公式

  1. $$\int x^n dx = \frac{x^{n+1}}{n+1} + C \quad (n \neq -1)$$

  2. $$\int \frac{1}{x} dx = \ln|x| + C$$

  3. $$\int e^x dx = e^x + C$$

  4. $$\int \sin x , dx = -\cos x + C$$

  5. $$\int \cos x , dx = \sin x + C$$

  6. $$\int \sec^2 x , dx = \tan x + C$$

泰勒展開式

【给我俩分钟,还你泰勒公式记忆一片天空】 https://www.bilibili.com/video/BV1bC4y1H7cp/?share_source=copy_web&vd_source=b38b089ffe2c29ef61bebcff0f458ed8

其實只需要記住

$e^x$

$sin x$

$ln(1+x)$

這三個就可以

$$ e^x = 1 + x + \frac{x^2}{2!} + \frac{x^3}{3!} + \frac{x^4}{4!} + \cdots + \frac{x^n}{n!} + o(x^n) $$

$$ \sin x = x - \frac{x^3}{3!} + \cdots + \frac{(-1)^n}{(2n+1)!} x^{2n+1} + o(x^{2n+1}) $$

$$ \cos x = 1 - \frac{x^2}{2!} + \cdots + \frac{(-1)^n}{(2n)!} x^{2n} + o(x^{2n}) $$

$$ \frac{1}{1 - x} = 1 + x + x^2 + x^3 + \cdots + x^n + o(x^n) $$

$$ \frac{1}{1 + x} = 1 - x + x^2 - x^3 + \cdots + (-1)^n x^n + o(x^n) $$

$$ \ln(1 + x) = x - \frac{x^2}{2} + \frac{x^3}{3} - \cdots + \frac{(-1)^{n-1}}{n} x^n + o(x^n) $$

Licensed under CC BY-NC-SA 4.0