−π2≤x≤π2\frac{-\pi}{2} \leq x \leq \frac{\pi}{2}2−π≤x≤2π
−π2<x<π2\frac{-\pi}{2}<x<\frac{\pi}{2}2−π<x<2π
0≤x≤π0 \leq x \leq \pi0≤x≤π
−π≤x≤π-\pi \leq x \leq \pi−π≤x≤π