公式独立成行，用$$包裹latex代码
行内公式，用左 latex，右 /latex包裹latex代码,（加上[ ]）

When $$ a \ne 0 $$, there are two solutions to \(ax^2 + bx + c = 0\) and they are
\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}.\)

标量场\(\varphi\)的梯度：

\({\rm grad}\varphi=\frac{\partial\varphi}{\partial x}e_1+\frac{\partial\varphi}{\partial y}e_2+\frac{\partial\varphi}{\partial z}e_3=\nabla\varphi\)

Thus we can write a vector \({\bf a}\in\mathbb {R}^2\)as

\({\bf a}=\left(\begin{matrix}a_1\\a_2\end{matrix}\right)\)

对应位置元素相加即可。

\(\left(\begin{matrix}a_1\\a_2\end{matrix}\right)+\left(\begin{matrix}b_1\\b_2\end{matrix}\right)=\left(\begin{matrix}a_1+b_1\\a_2+b_2\end{matrix}\right)\)

范数以及标准化
欧几里得范数（Euclidean Vector Norm）
For a vector \({\bf v}\in\mathbb{ R}^n\),the euclidean norm of \(\mathbf{v}\)is defined as,
\(\parallel\mathbf{v}\parallel=\left(\sum_{i=1}^{n}{v_i^2}\right)^\frac{1}{2}=\sqrt{\left\langle \mathbf{v,v}\right\rangle} \)

\(\boxed{\vec{s}}\) , \(\overrightarrow{suv}\)

import matplotlib.pyplot as plt
import numpy as np

x=np.linspace(0,20,100)
plt.plot(x, np.sin(x))
plt.show()