99+2-1=100 \\
x^2+2x+5+\sqrt x=0 \\
\begin{cases}
x+y+z=10 \\
x+2y+3z=20 \\
x+4y+5z=30
\end{cases} \\
\sum_{i=1}^{N}2i+1 \\
\prod\limits_{i=1}^n{2i} \\
\frac{1}{2x^2+2ax+1} \\
9 \times 8 = 72 \\
5 \cdot 6 = 30 \\
30 \div 6 = 5 \\
y=\begin{cases}
x^2, & x>0 \\
x^2+x-8, & x \le 6 \\
x^3, & other \\
\end{cases} \\
A=\left[
\begin{array}{c c c : c}
1 & 2 & 3 & 4 \\
5 & 6 & 7 & 8 \\
9 & 10 & 11 & 12 \\
\end{array}
\right] \\
欧拉方程：& e^{i\pi}+1=0 \\
质能守恒：& E=mc^2 \\
万有引力：& F=G \frac {m_1 m_2}{R^2} \\
麦克斯韦方程组： \\
\begin{array}{lll}
\nabla\times E &=& -\;\frac{\partial{B}}{\partial{t}} \\
\ \nabla\times H &=& \frac{\partial{D}}{\partial{t}}+J \\
\ \nabla\cdot D &=& \rho
\ \nabla\cdot B &=& 0
\ \end{array}$ \\
薛定谔方程：\\
\hbar\frac
{\partial \psi}
{\partial t}
= \frac{-\hbar^2}{2m} \left(\frac{\partial^2}
{\partial x^2} + \frac{\partial^2}
{\partial y^2}+\frac{\partial^2}
{\partial z^2}
\right) \psi + V \psi$
语调符号：\\
\text{\={a}} & 一声\\
\text{\'{a}} & 二声\\
\text{\v{a}} & 三声\\
\text{\`{a}} & 四声\\
\text{\u{a}} & \\
\text{\~{a}} & \\
\text{\.u{a}} & \\
\text{\^{a}} & \\
\text{\"{a}} & \\
\text{\r{a}} & \\
\text{a} & 轻声\\