数学公式备忘
用 Sympy 求解是不错的选择
微积分
导数
\[\begin{aligned} (\operatorname{tg} x)^{\prime} & =\sec ^2 x & (\arcsin x)^{\prime} & =\frac{1}{\sqrt{1-x^2}} \\ (\operatorname{ctg} x)^{\prime} & =-\csc ^2 x & (\arccos x)^{\prime} & =-\frac{1}{\sqrt{1-x^2}} \\ (\sec x)^{\prime} & =\sec x \cdot \operatorname{tg} x & (\operatorname{arctg} x)^{\prime} & =\frac{1}{1+x^2} \\ (\csc x)^{\prime} & =-\csc x \cdot \operatorname{ctg} x & (\operatorname{arcctg} x)^{\prime} & =-\frac{1}{1+x^2} \\ \left(a^x\right)^{\prime} & =a^x \ln a & & \end{aligned} \]
运算法则(导数表):
\[\begin{aligned} \frac{\mathrm{d}}{\mathrm{d} x}(f+g) & =\frac{\mathrm{d} f}{\mathrm{~d} x}+\frac{\mathrm{d} g}{\mathrm{~d} x} & \frac{\mathrm{d}}{\mathrm{d} x}[f(g(x))] & =\frac{\mathrm{d} f}{\mathrm{~d} g} \cdot \frac{\mathrm{d} g}{\mathrm{~d} x}=f^{\prime}(g(x)) \cdot g^{\prime}(x) \\ \frac{\mathrm{d}}{\mathrm{d} x}(c \cdot f) & =c \cdot \frac{\mathrm{d} f}{\mathrm{~d} x} & \frac{\mathrm{d}^n}{\mathrm{~d} x^n} f(x) g(x) & =\sum_{i=0}^n\left(\begin{array}{c} n \\ i \end{array}\right) f^{(n-i)}(x) g^{(i)}(x) \\ \frac{\mathrm{d}}{\mathrm{d} x}(f \cdot g) & =f \cdot \frac{\mathrm{d} g}{\mathrm{~d} x}+g \cdot \frac{\mathrm{d} f}{\mathrm{~d} x} & \frac{\mathrm{d}}{\mathrm{d} x}\left(\frac{1}{f}\right) & =-\frac{f^{\prime}}{f^2} \\ \frac{\mathrm{d}}{\mathrm{d} x}\left(\frac{f}{g}\right) & =\frac{-f \cdot \frac{\mathrm{d} g}{d x}+g \cdot \frac{\mathrm{d} f}{\mathrm{~d} x}}{g^2} & & \end{aligned} \]
积分
\[\begin{array}{ll} \int k \mathrm{~d} x=k x+C(k \text { 是常数 }), & \int \frac{\mathrm{d} x}{\sqrt{1-x^2}}=\arcsin x+C, \\ \int x^{\prime \prime} \mathrm{d} x=\frac{x^{\mu+1}}{\mu+1}+C(\mu \neq-1), & \int a^x \mathrm{~d} x=\frac{a^x}{\ln a}+C, \\ \int \frac{\mathrm{d} x}{x}=\ln |x|+C, & \int \cos x \mathrm{~d} x=\sin x+C, \\ \int \frac{\mathrm{d} x}{1+x^2}=\arctan x+C, & \int \sin x \mathrm{~d} x=-\cos x+C, \end{array} \]
运算法则:
\[\begin{aligned} \int c \cdot f(x) \mathrm{d} x & =c \cdot \int f(x) \mathrm{d} x \\ \int(f(x) \pm g(x)) \mathrm{d} x & =\int f(x) \mathrm{d} x \pm \int g(x) \mathrm{d} x \\ \int u d v & =u v-\int v d u \end{aligned} \]
泰勒级数
\[f(a)+\frac{f^{\prime}(a)}{1 !}(x-a)+\frac{f^{\prime \prime}(a)}{2 !}(x-a)^2+\frac{f^{\prime \prime \prime}(a)}{3 !}(x-a)^3+\cdots=\sum_{n=0}^{\infty} \frac{f^{(n)}(a)}{n !}(x-a)^n \]
\[\begin{aligned} \ln (1+x) & =\sum_{k=1}^{\infty}(-1)^{k+1} \frac{x^k}{k}(-1 \lt x \leq 1) & \ln (1-x) & =-\sum_{k=1}^{\infty} \frac{x^k}{k}(-1 \leq x \lt 1) \\ \frac{1}{1-x} & =\sum_{n=0}^{\infty} x^n & \frac{1}{1+x} & =\sum_{n=0}^{\infty}(-1)^n x^n \\ e^x & =\sum_{k=0}^{\infty} \frac{x^k}{k !} & \sin x & =\sum_{n=0}^{\infty}(-1)^n \frac{x^{2 n+1}}{(2 n+1) !} \end{aligned} \]
复变函数与积分变换
拉普拉斯变换
\[\begin{gathered}\mathscr{L}[f(t)]=F(s)=\int_0^{\infty} f(t) \mathrm{e}^{-t} \mathrm{~d} t \\ \mathscr{L}^{-1}[F(s)]=f(t)=\frac{1}{2 \pi \mathrm{j}} \int_{\sigma-\mathrm{j} \infty}^{\sigma+\mathrm{j} \infty} F(s) \mathrm{e}^{s t} \mathrm{~d} s\end{gathered} \]
运算法则
\[\begin{array}{|c|c|} \hline \text { Time domain } & s \text { domain } \\ \hline a f(t)+b g(t) & a F(s)+b G(s) \\ \hline t f(t) & -F^{\prime}(s) \\ \hline t^n f(t) & (-1)^n F^{(n)}(s) \\ \hline f^{\prime}(t) & s F(s)-f\left(0^{-}\right) \\ \hline f^{\prime \prime}(t) & s^2 F(s)-s f\left(0^{-}\right)-f^{\prime}\left(0^{-}\right) \\ \hline f^{(n)}(t) & s^n F(s)-\sum_{k=1}^n s^{n-k} f^{(k-1)}\left(0^{-}\right) \\ \hline \frac{1}{t} f(t) & \int_s^{\infty} F(\sigma) d \sigma \\ \hline \int_0^t f(\tau) d \tau=(u * f)(t) & \frac{1}{s} F(s) \\ \hline e^{a t} f(t) & F(s-a) \\ \hline f(t-a) u(t-a) & e^{-a s} F(s) \\ \hline f(t) u(t-a) & e^{-a s} \mathcal{L}\{f(t+a)\} \\ \hline f(a t) & \frac{1}{a} F\left(\frac{s}{a}\right) \\ \hline f(t) g(t) & \frac{1}{2 \pi i} \lim _{T \rightarrow \infty} \int_{c-i T}^{c+i T} F(\sigma) G(s-\sigma) d \sigma \\ \hline(f * g)(t)=\int_0^t f(\tau) g(t-\tau) d \tau & F(s) \cdot G(s) \\ \hline(f * g)(t)=\int_0^T f(\tau) g(t-\tau) d \tau & F(s) \cdot G(s) \\ \hline f^*(t) & F^*\left(s^*\right) \\ \hline(f \star g)(t)=\int_0^{\infty} f(\tau)^* g(t+\tau) d \tau & F^*\left(-s^*\right) \cdot G(s) \\ \hline f(t) & \frac{1}{1-e^{-T s}} \int_0^T e^{-s t} f(t) d t \\ \hline \begin{array}{l} f_P(t)=\sum_{n=0}^{\infty} f(t-T n) \\ f_P(t)=\sum_{n=0}^{\infty}(-1)^n f(t-T n) \end{array} & \begin{array}{l} F_P(s)=\frac{1}{1-e^{-T s}} F(s) \\ F_P(s)=\frac{1}{1+e^{-T s}} F(s) \end{array} \\ \hline \end{array} \]
常见变换
\[\begin{array}{|c|c|c|} \hline \begin{array}{c} \text { Time domain } \\ f(t)=\mathcal{L}^{-1}\{F(s)\} \end{array} & \begin{array}{l} \text { Laplace s-domain } \\ F(s)=\mathcal{L}\{f(t)\} \end{array} & \begin{array}{l} \text { Region of } \\ \text { convergence } \end{array} \\ \hline \delta(t) & 1 & \text { all } s \\ \hline \delta(t-\tau) & e^{-\tau s} & \\ \hline u(t) & \frac{1}{s} & \operatorname{Re}(s)>0 \\ \hline u(t-\tau) & \frac{1}{s} e^{-\tau s} & \operatorname{Re}(s)>0 \\ \hline f(t-\tau) u(t-\tau) & e^{-s \tau} \mathcal{L}\{f(t)\} & \\ \hline u(t)-u(t-\tau) & \frac{1}{s}\left(1-e^{-\tau s}\right) & \operatorname{Re}(s)>0 \\ \hline t \cdot u(t) & \frac{1}{s^2} & \operatorname{Re}(s)>0 \\ \hline t^n \cdot u(t) & \frac{n !}{s^{n+1}} & \begin{array}{c} \operatorname{Re}(s)>0 \\ (n>-1) \end{array} \\ \hline t^q \cdot u(t) & \frac{\Gamma(q+1)}{s^{q+1}} & \begin{array}{c} \operatorname{Re}(s)>0 \\ \operatorname{Re}(q)>-1 \end{array} \\ \hline \sqrt[n]{t} \cdot u(t) & \frac{1}{s^{\frac{1}{n}+1}} \Gamma\left(\frac{1}{n}+1\right) & \operatorname{Re}(s)>0 \\ \hline t^n e^{-\alpha t} \cdot u(t) & \frac{n !}{(s+\alpha)^{n+1}} & \operatorname{Re}(s)>-\alpha \\ \hline(t-\tau)^n e^{-\alpha(t-\tau)} \cdot u(t-\tau) & \frac{n ! \cdot e^{-\tau s}}{(s+\alpha)^{n+1}} & \operatorname{Re}(s)>-\alpha \\ \hline e^{-\alpha t} \cdot u(t) & \frac{1}{s+\alpha} & \operatorname{Re}(s)>-\alpha \\ \hline e^{-\alpha|t|} & \frac{2 \alpha}{\alpha^2-s^2} & -\alpha<\operatorname{Re}(s)<\alpha \\ \hline\left(1-e^{-\alpha t}\right) \cdot u(t) & \frac{\alpha}{s(s+\alpha)} & \operatorname{Re}(s)>0 \\ \hline \sin (\omega t) \cdot u(t) & \frac{\omega}{s^2+\omega^2} & \operatorname{Re}(s)>0 \\ \hline \cos (\omega t) \cdot u(t) & \frac{s}{s^2+\omega^2} & \operatorname{Re}(s)>0 \\ \hline \sinh (\alpha t) \cdot u(t) & \frac{\alpha}{s^2-\alpha^2} & \operatorname{Re}(s)>|\alpha| \\ \hline \cosh (\alpha t) \cdot u(t) & \frac{s}{s^2-\alpha^2} & \operatorname{Re}(s)>|\alpha| \\ \hline e^{-\alpha t} \sin (\omega t) \cdot u(t) & \frac{\omega}{(s+\alpha)^2+\omega^2} & \operatorname{Re}(s)>-\alpha \\ \hline e^{-\alpha t} \cos (\omega t) \cdot u(t) & \frac{s+\alpha}{(s+\alpha)^2+\omega^2} & \operatorname{Re}(s)>-\alpha \\ \hline \ln (t) \cdot u(t) & -\frac{1}{s}[\ln (s)+\gamma] & \operatorname{Re}(s)>0 \\ \hline J_n(\omega t) \cdot u(t) & \frac{\left(\sqrt{s^2+\omega^2}-s\right)^n}{\omega^n \sqrt{s^2+\omega^2}} & \begin{array}{c} \operatorname{Re}(s)>0 \\ (n>-1) \end{array} \\ \hline \operatorname{erf}(t) \cdot u(t) & \frac{1}{s} e^{(1 / 4) s^2}\left(1-\operatorname{erf} \frac{s}{2}\right) & \operatorname{Re}(s)>0 \\ \hline \end{array} \]
拉氏变换与积分
参考 / 3,利用拉氏变换定义可证明如下公式。只有反常积分存在且收敛才可套用如下公式:
\[\begin{aligned} &\int_0^{+\infty} f(t) \mathrm{d} t=F(0)\\ &\int_0^{+\infty} t f(t) \mathrm{d} t=-F^{\prime}(0)\\ &\int_0^{+\infty} \frac{f(t)}{t} \mathrm{~d} t=\int_0^{\infty} F(s) \mathrm{d} s \end{aligned} \]
线代&矩阵
参考:线性代数公式定理一览表 /
行列式
代数余子式展开(\(A_{i j}=(-1)^{i+j} M_{i j}\)):
\[\begin{aligned} &D=a_{i 1} A_{i 1}+a_{i 2} A_{i 2}+\cdots+a_{i n} A_{i n}=\sum_{k=1}^n a_{i k} A_{i k} \quad(i=1,2, \ldots, n)\\ &D=a_{1 j} A_{1 j}+a_{2 j} A_{2 j}+\cdots+a_{n j} A_{n j}=\sum_{k=1}^n a_{k j} A_{k j} \quad(j=1,2, \ldots, n) \end{aligned} \]
范德蒙德
\[D_n=\left|\begin{array}{cccc} 1 & 1 & \ldots & 1 \\ x_1 & x_2 & \ldots & x_n \\ x_1^2 & x_2^2 & \ldots & x_n^2 \\ \vdots & \vdots & & \vdots \\ x_1^{n-1} & x_2^{n-1} & \ldots & x_n^{n-1} \end{array}\right|=\prod_{1 \leq i \lt j \leq n}\left(x_j-x_i\right) \]
矩阵转置&逆&正交
转置
- \((\lambda A)^T=\lambda A^T\)
- \((A \pm B)^T=A^T \pm B^T\)
- \((A B)^T=B^T A^T\)
- 设 \(A\) 是 \(n\) 阶方阵, 则 \(\left|A^T\right|=|A|\)
- \(\left(A^T\right)^T=A\)
逆
- 当 \(\lambda\) 是非零实数时, \(\lambda A\) 也可逆, 且 \((\lambda A)^{-1}=\frac{1}{\lambda} A^{-1}\)
- \(A B\) 可逆, 且 \((A B)^{-1}=B^{-1} A^{-1}\)
- \(A^T\) 可逆, 且 \(\left(A^T\right)^{-1}=\left(A^{-1}\right)^T\)
- \(A^{-1}\) 可逆, 且 \(\left(A^{-1}\right)^{-1}=A,\left|A^{-1}\right|=\frac{1}{|A|}\)
- \(A^*\) 可逆, 且 \(\left(A^*\right)^{-1}=\left(A^{-1}\right)^*=\frac{A}{|A|}, A^*=|A| A^{-1},\left|A^*\right|=|A|^{n-1}\)
已知 \(A\) 为正交矩阵则
- \(A^{-1}=A^T\) 也是正交阵;
- \(|A|= \pm 1\)
- 若 \(B\) 也是正交阵, 则 \(A B\) 也是正交阵;
- \(A\) 的行(列)向量组构成 \(R^n\) 的一个标准正交基.
LaTeX
\(\LaTeX\)($\LaTeX$)示例,更多细节可以参考第三章
希腊字符
| LaTex | \(\LaTeX\) | LaTex | \(\LaTeX\) | LaTex | \(\LaTeX\) | LaTex | \(\LaTeX\) | 
|---|---|---|---|---|---|---|---|
| \alpha | \(\alpha\) | \nu | \(\nu\) | \digamma | \(\digamma\) | \Pi | \(\Pi\) | 
| \beta | \(\beta\) | \kappa | \(\kappa\) | \varkappa | \(\varkappa\) | \Psi | \(\Psi\) | 
| \gamma | \(\gamma\) | \lambda | \(\lambda\) | \varpi | \(\varpi\) | \varrho | \(\varrho\) | 
| \delta | \(\delta\) | \mu | \(\mu\) | \varsigma | \(\varsigma\) | \Sigma | \(\Sigma\) | 
| \epsilon | \(\epsilon\) | \zeta | \(\zeta\) | \eth | \(\eth\) | \phi | \(\phi\) | 
| \eta | \(\eta\) | \theta | \(\theta\) | \upsilon | \(\upsilon\) | \varphi | \(\varphi\) | 
| \iota | \(\iota\) | \xi | \(\xi\) | \chi | \(\chi\) | \psi | \(\psi\) | 
| \pi | \(\pi\) | \rho | \(\rho\) | \omega | \(\omega\) | \vartheta | \(\vartheta\) | 
| \sigma | \(\sigma\) | \tau | \(\tau\) | \Omega | \(\Omega\) | \hbar | \(\hbar\) | 
| \Gamma | \(\Gamma\) | \Delta | \(\Delta\) | \varepsilon | \(\varepsilon\) | \Upsilon | \(\Upsilon\) | 
| \Lambda | \(\Lambda\) | \Phi | \(\Phi\) | \Xi | \(\Xi\) | \Theta | \(\Theta\) | 
其他符号
| LaTex | \(\LaTeX\) | LaTex | \(\LaTeX\) | LaTex | \(\LaTeX\) | LaTex | \(\LaTeX\) | 
|---|---|---|---|---|---|---|---|
| \partial | ∂ | \infty | \(\infty\) | \nrightarrow | \(\nrightarrow\) | \mapsto | \(\mapsto\) | 
| \wedge | ∧ | \vee | \(\vee\) | \geq | \(\geq\) | \leq | \(\leq\) | 
| \neg | \(\neg\) | \pm | \(\pm\) | \equiv | \(\equiv\) | \sim | \(\sim\) | 
| \bot | \(\bot\) | \top | ⊤ | \gg | \(\gg\) | \ll | \(\ll\) | 
| \nabla | \(\nabla\) | \varnothing | ∅ | \subset | ⊂ | \subseteq | \(\subseteq\) | 
| \angle | \(\angle\) | \measuredangle | \(\measuredangle\) | \in | ∈ | \notin | \(\notin\) | 
| \surd | \(\surd\) | \forall | \(\forall\) | \mid | \(\mid\) | \propto | \(\propto\) | 
| \exists | \(\exists\) | \nexists | \(\nexists\) | \perp | \(\perp\) | ||
| \hookrightarrow | ↪ | \Rightarrow | ⇒ | \vartriangle | \(\vartriangle\) | ||
| \int | \(\int\) | \iint | \(\iint\) | \bigcup | \(\bigcup\) | ||
| \iiint | \(\iiint\) |  \parallel | \(\parallel\) | \bigcap | \(\bigcap\) | a a\ b | \(a a\ b\) | 
| \prod | \(\prod\) | \sum | \(\sum\) | \simeq | \(\simeq\) | a\quad b | \(a\quad b\) | 
| \rightarrow | \(\rightarrow\) | \Leftrightarrow | ⇔ | \iff | \(\iff\) | a\qquad b | \(a\qquad b\) | 
数学标记
| LaTex | \(\LaTeX\) | 英文读法 | LaTex | \(\LaTeX\) | 英文读法 | 
|---|---|---|---|---|---|
| x'/x^{\prime} | \(x^{\prime}\) | \(x\) prime | x_i | \(x_i\) | \(x\) subscript \(\mathrm{i}, x\) sub \(\mathrm{i}\) | 
| x'' | \(x^{\prime \prime}\) | \(x\) double prime | x^i | \(x^i\) | \(x\) to the \(\mathrm{n}, x\) to the nth | 
| \overrightarrow{AB} | \(\overrightarrow{A B}\) | vec pointing from \(A\) to \(B\) | \ddot{x} | \(\ddot{x}\) | \(x\) double dot | 
| \underline{x} | \(\underline{x}\) | \(x\) underline | x^* | \(x^*\) | \(x\) star, \(x\) super asterisk | 
| \hat{x} | \(\hat{x}\) | \(x\) hat | x\dagger | \(x \dagger\) | \(x\) dagger | 
| \bar{x} | \(\bar{x}\) | \(x\) bar | x\ddagger | \(x \ddagger\) | \(x\) double dagger | 
| \dot{x} | \(\dot{x}\) | \(x\) dot | {\color{red}x} | \({\color{red}x}\) | red \({\color{red}x}\) | 
| \tilde{x} | \(\tilde{x}\) | \(x\) tilde | 
字母样式
| Latex | \(\LaTeX\) | 说明 | 
|---|---|---|
| {AaBbCc} | \({AaBbCc}\) | 斜体, 大部分数学符号、表达式 | 
| \mathrm {AaBbCc} | \(\mathrm {AaBbCc}\) | 正体, 公式中的单位或文字 | 
| \mathbf{AaBbCc} | \(\mathbf{AaBbCc}\) | 粗体, 向量、矩阵 | 
| \boldsymbol {AaBbCc} | \(\boldsymbol {AaBbCc}\) | 粗体、斜体, 向量、矩阵 | 
| \mathtt {AaBbCc} | \(\mathtt {AaBbCc}\) | 等宽字体, 常用于代码 | 
| \mathcal {AaBbCc} | \(\mathcal{A B C D E F}\) | 花体, 用于表示数学中的集合、代数结构、算子 | 
| \mathbb {AaBbCc} | \(\mathbb {AaBbCc}\) | 黑板粗体 (blackboard bold), 常用来表达各种集合 | 
| \text {Aa Bb Cc} | \(\text {Aa Bb Cc}\) | 用来写公式中的文字 | 
| \mathrm{d}x | \(\mathrm{d}x\) | ISO 规定导数符号 \(\mathrm{d}\) 为正体 | 
| \operatorname{T} | \(\operatorname{T}\) | 运算符 |