markdown常用数学公式

$$ f(x)=x $$

$$ 
\sum_i^n + 
\sum_{i=0}^{n} 
$$

$$ x^2 + x_i $$

$$ \lbrace a+x \rbrace $$

$$
f(x)=\begin{cases} 
		1, & x>0\\ 
		0, & x=0\\
		-1, & x<0
\end{cases}
$$

$$ \langle x \rangle $$

$$ \lceil \frac{x}{2} \rceil $$

$$ \lfloor x \rfloor $

$$
    \lbrace  \sum_{i=0}^{n}i^{2}=\frac{2a}{x^2+1}   \rbrace
$$

$$  
\left\lbrace 
\sum_{i=0}^{n}i^{2}=\frac{2a}{x^2+1}                            
\right\rbrace 
$$

$$ \int_{1}^{\infty} $$

$$
\prod_{1}^{n} +
\bigcup_{1}^{n} +
\iint_{1}^{n}
$$

$$
\frac ab + \frac{1}{2} + {a+1 \over b+1}
$$

$$
\sqrt[x+1 ]{(x+1)^2}
$$

$$ \lim_{x\to +\infty} $$

$$ x_n\stackrel{p}\longrightarrow0 $$

$$ \vec{a} + \overrightarrow{a} $$

$$ \hat y=a\hat x+b $$

$$ \mathtt{X}' $$

$$
  \begin{matrix}
   1 & 2 & 3 \\
   4 & 5 & 6 \\
   7 & 8 & 9
  \end{matrix} \tag{1}
$$

$$
 \left\{
 \begin{matrix}
   1 & 2 & 3 \\
   4 & 5 & 6 \\
   7 & 8 & 9
  \end{matrix}
  \right\} \tag{2}
$$

$$
 \left[
 \begin{matrix}
   1 & 2 & 3 \\
   4 & 5 & 6 \\
   7 & 8 & 9
  \end{matrix}
  \right] \tag{3}
$$

$$
\left[
\begin{matrix}
 1      & 2      & \cdots & 4      \\
 7      & 6      & \cdots & 5      \\
 \vdots & \vdots & \ddots & \vdots \\
 8      & 9      & \cdots & 0      \\
\end{matrix}
\right] \tag{4}
$$

$$ 
\left[
    \begin{array}{cc|c}
      1 & 2 & 3 \\
      4 & 5 & 6
    \end{array}
\right] \tag{5}
$$

$$
\begin{aligned}
a &= b + c\\
  &= d + e + f
\end{aligned}
$$

$$
  \prod_{{
  \begin{gathered}
            1\le i \le n\\
            1\le j \le m
  \end{gathered}
            }}
     M_{i,j}
$$

$$
\begin{aligned}
 \boxed{x^2+y^2 = z^2}
\end{aligned}
$$

$$
z = \overbrace{
   \underbrace{x}_\text{real} + i
   \underbrace{y}_\text{imaginary}
  }^\text{complex number}
$$

$$ 
\sum \\
\div \\
\cdot \\
\ast \\
\bigotimes \\
\bigoplus \\
\cdots \\
\lambda \\
\mu \\
\theta \\
\pi \\
\notin \\
\times
$$