标签：begin over end case style amp margin nbsp dir
$$\begin{equation}R_a(x)=\begin{cases}0&\mbox{ x<-a or x>a}\\ {1\over 2a}&\mbox{-a<x<a}\end{cases}\end{equation}$$
标签：begin over end case style amp margin nbsp dir
原文地址：https://www.cnblogs.com/mqiyang/p/9276252.html
