2nπ+π22 n \pi+\frac{\pi}{2}2nπ+2π
2nπ−π22 n \pi-\frac{\pi}{2}2nπ−2π
nπ+π2\mathrm{n} \pi+\frac{\pi}{2}nπ+2π
nπ−π2n \pi-\frac{\pi}{2}nπ−2π