摘要：
1. Monica: There's nothing to tell! He's just some guy I work with! Joey: C'mon, you're going out with the guy! There's gotta be something wrong with 阅读全文
摘要：
$$\begin{equation}R_a(x)=\begin{cases}0&\mbox{ x<-a or x>a}\\ {1\over 2a}&\mbox{-a<x<a}\end{cases}\end{equation}$$ 阅读全文