latex测试先不要删除¶

##### 行内的公式 Inline
 
$$E=mc^2$$

Inline 行内的公式 $$E=mc^2$$ 行内的公式，行内的$$E=mc^2$$公式。

$$c = \\pm\\sqrt{a^2 + b^2}$$

$$x > y$$

$$f(x) = x^2$$

$$\alpha = \sqrt{1-e^2}$$

$$$\sqrt{3x-1}+(1+x)^2$$$
             
$$\sin(\alpha)^{\theta}=\sum_{i=0}^{n}(x^i + \cos(f))$$

$$\\dfrac{-b \\pm \\sqrt{b^2 - 4ac}}{2a}$$

$$f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$

$$\displaystyle \frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{\frac25 \pi}} = 1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {1+\frac{e^{-6\pi}} {1+\frac{e^{-8\pi}} {1+\cdots} } } }$$

$$\displaystyle \left( \sum\_{k=1}^n a\_k b\_k \right)^2 \leq \left( \sum\_{k=1}^n a\_k^2 \right) \left( \sum\_{k=1}^n b\_k^2 \right)$$

$$a^2$$

$$a^{2+2}$$

$$a_2$$

$${x_2}^3$$

$$x_2^3$$

$$10^{10^{8}}$$

$$a_{i,j}$$

$$_nP_k$$

$$c = \pm\sqrt{a^2 + b^2}$$

$$\frac{1}{2}=0.5$$

$$\dfrac{k}{k-1} = 0.5$$

$$\dbinom{n}{k} \binom{n}{k}$$

$$\oint_C x^3\, dx + 4y^2\, dy$$

$$\bigcap_1^n p   \bigcup_1^k p$$

$$e^{i \pi} + 1 = 0$$

$$\left ( \frac{1}{2} \right )$$

$$x_{1,2}=\frac{-b\pm\sqrt{\color{Red}b^2-4ac}}{2a}$$

$${\color{Blue}x^2}+{\color{YellowOrange}2x}-{\color{OliveGreen}1}$$

$$\textstyle \sum_{k=1}^N k^2$$

$$\dfrac{ \tfrac{1}{2}[1-(\tfrac{1}{2})^n] }{ 1-\tfrac{1}{2} } = s_n$$

$$\binom{n}{k}$$

$$0+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+\cdots$$

$$\sum_{k=1}^N k^2$$

$$\textstyle \sum_{k=1}^N k^2$$

$$\prod_{i=1}^N x_i$$

$$\textstyle \prod_{i=1}^N x_i$$

$$\coprod_{i=1}^N x_i$$

$$\textstyle \coprod_{i=1}^N x_i$$

$$\int_{1}^{3}\frac{e^3/x}{x^2}\, dx$$

$$\int_C x^3\, dx + 4y^2\, dy$$

$${}_1^2\!\Omega_3^4$$

##### 多行公式 Multi line

> \`\`\`math or \`\`\`latex or \`\`\`katex

```math
f(x) = \int_{-\infty}^\infty
    \hat f(\xi)\,e^{2 \pi i \xi x}
    \,d\xi
```

```math
\displaystyle
\left( \sum\_{k=1}^n a\_k b\_k \right)^2
\leq
\left( \sum\_{k=1}^n a\_k^2 \right)
\left( \sum\_{k=1}^n b\_k^2 \right)
```

```math
\dfrac{ 
    \tfrac{1}{2}[1-(\tfrac{1}{2})^n] }
    { 1-\tfrac{1}{2} } = s_n
```

```katex
\displaystyle 
    \frac{1}{
        \Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{
        \frac25 \pi}} = 1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {
        1+\frac{e^{-6\pi}}
        {1+\frac{e^{-8\pi}}
         {1+\cdots} }
        } 
    }
```

```latex
f(x) = \int_{-\infty}^\infty
    \hat f(\xi)\,e^{2 \pi i \xi x}
    \,d\xi
```