我个人很喜欢在 emacs 里用 latex 写公式，而且可以从中到处对应的 pdf ，很方便。在这里我记录一下常用的代码。

公式代 展示效果
\times \(\times\)
\rightarrow \(\rightarrow\)
A_{x} \(A_{x}\)
A^{x} \(A^{x}\)
\mbox{汉语} \(\mbox{汉语}\)
\geq \(\geq\)
a\qquad b(a b 之间留空) \(a \qquad{b}\)
\overline{CS} \(\overline{CS}\)
\underline{CS} \(\underline{CS}\)
\neq \(\neq\)
\leq \(\leq\)
\sqrt{x} \(\sqrt{x}\)
\underbrace{a+b\cdots+z}_{26} \(\underbrace{a+b\cdots+z}_{26}\)
\vec a \quad \overrightarrow{AB} \(\vec a \quad \overrightarrow{AB}\)
\sum_{i=1}^{n} aa \(\sum_{i=1}^{n} aa\)
\int_{0}^{5} \(\int_{0}^{5}\)
\in \(\in\)
\frac{5}{\pi} \(\frac{5}{\pi}\)
\hat{C} \(\hat{C}\)
\forall \(\forall\)
\exists \(\exists\)
\partial \(\partial\)
\mathcal{L} \(\mathcal{L}\)

多行的不太好用表格表示：

向量，

\mathbf{x} = \left[ \\
\begin{matrix}
a_1 \\
a_2 \\
\vdots \\
a_n \\
\end{matrix}
\right], \tag{1, 1}

\[ \mathbf{x} = \left[ \\ \begin{matrix} a_1 \\ a_2 \\ \vdots \\ a_n \\ \end{matrix} \right], \tag{1, 1} \]

矩阵，

\mathbf{x} = \left[
\begin{matrix}
a_{11} & a_{12} & \dots & a_{1n} \\
a_{21} & a_{22} & \dots & a_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
a_{m1} & a_{m2} & \dots & a_{mn} \\
\end{matrix}
\right], \tag{2, 1}

\[ \mathbf{x} = \left[ \begin{matrix} a_{11} & a_{12} & \dots & a_{1n} \\ a_{21} & a_{22} & \dots & a_{2n} \\ \vdots & \vdots & \ddots & \vdots \\ a_{m1} & a_{m2} & \dots & a_{mn} \\ \end{matrix} \right], \tag{2, 1} \]

转置，

\mathbf{A} = \mathbf{A^{\mathrm{T}}}

\[ \mathbf{A} = \mathbf{A^{\mathrm{T}}} \]

哈达玛积，

\mathbf{A} \odot \mathbf{B} = \left[
\begin{matrix}
a_{11}b_{11} & a_{12}b_{12} & \dots & a_{1n}b_{1n} \\
a_{21}b_{21} & a_{22}b_{22} & \dots & a_{2n}b_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
a_{m1}b_{m1} & a_{m2}b_{m2} & \dots & a_{mn}b_{mn} \\
\end{matrix}
\right], \tag{3, 1}

\[ \mathbf{A} \odot \mathbf{B} = \left[ \begin{matrix} a_{11}b_{11} & a_{12}b_{12} & \dots & a_{1n}b_{1n} \\ a_{21}b_{21} & a_{22}b_{22} & \dots & a_{2n}b_{2n} \\ \vdots & \vdots & \ddots & \vdots \\ a_{m1}b_{m1} & a_{m2}b_{m2} & \dots & a_{mn}b_{mn} \\ \end{matrix} \right], \tag{3, 1} \]

矩阵向量积，

\mathbf{A} = \left[
\begin{matrix}
\mathbf{a_1^{\mathsf{T}}} \\
\mathbf{a_2^{\mathsf{T}}} \\
\vdots \\
\mathbf{a_m^{\mathsf{T}}} \\
\end{matrix}
\right] \tag{4, 1}

\[ \mathbf{A} = \left[ \begin{matrix} \mathbf{a_1^{\mathsf{T}}} \\ \mathbf{a_2^{\mathsf{T}}} \\ \vdots \\ \mathbf{a_m^{\mathsf{T}}} \\ \end{matrix} \right] \tag{4, 1} \]

大括号，

\[ \hat{C}'_p(x) \left\{ \begin{array}{lr} =\mu_w, & if & x_p > 0 \\ \\ \geq \mu_w, & if & x_p = 0, \end{array} \right. \]

以上，以后有新的再添加。