整理一些使用过的比较难记的latex语法，好记性不如烂笔头，根据使用记录慢慢补充：
排版
对齐
\begin {aligned}
line1 \\
line2 \\
... \\
lineN \\
\end{aligned}
每行公式行首似乎要加&才能相互对齐，对比如下：
不加&:
= l i n e 1 = l i n e 2 l i n e 2 l i n e 2 l i n e 2 = . . . = l i n e N l i n e N \begin {aligned} =line1 \\ =line2line2line2line2 \\ =... \\ =lineNlineN \\ \end{aligned} =line1=line2line2line2line2=...=lineNlineN
加&:
= l i n e 1 = l i n e 2 l i n e 2 l i n e 2 l i n e 2 = . . . = l i n e N l i n e N \begin {aligned} &=line1 \\ &=line2line2line2line2 \\ &=... \\ &=lineNlineN \\ \end{aligned} =line1=line2line2line2line2=...=lineNlineN
运算符
分数
\frac {a} {b} a b \frac {a} {b} ba