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 |