不写了，直接查表去吧
$\sum_{i=0}^N\int_{a}^{b}g(t,i)\text{d}t$
\[\sum_{i=0}^N\int_{a}^{b}g(t,i)\text{d}t\]你好\(\displaystyle\sum_{i=0}^N\int_{a}^{b}g(t,i)\text{d}t\)
看看这里 \(\sum_{i=0}^{N}\int_{a}^{b}g(t,i)\text{d}t\) 不错的
怎么这个公式在手机上显示不全
\[\begin{bmatrix} E_x\\ E_y\\ H_x\\ H_y\\ \end{bmatrix}=\frac{1}{k_c^2} \begin{bmatrix} -\gamma&0&0&-j\omega\mu\\ 0&-\gamma&j\omega\mu&0\\ 0&j\omega\epsilon&-\gamma&-j\omega\mu\\ -j\omega\epsilon&0&0&-\gamma\\ \end{bmatrix} \begin{bmatrix} \frac {\partial E_z}{\partial x}&\frac {\partial E_z}{\partial x}\\ \frac {\partial E_z}{\partial y}\\ \frac {\partial E_z}{\partial x}\\ \frac {\partial E_z}{\partial y}\\ \end{bmatrix}\]