Question

{α|α=2kπ±π/2,k∈Z}={β|β=kπ+π/2,k∈Z}为什么啊?

Answer 1

β=kπ+π/2,k∈Z
（1）k为偶数 β=2nπ+π/2,n∈Z
（2）k为奇数 β=（2n-1）π+π/2=2nπ-π/2,n∈Z
所以 {α|α=2kπ±π/2,k∈Z}={β|β=kπ+π/2,k∈Z}