kπ－π/2<2x＋π/4(kπ)/2－3π/8定义域是：(kπ/2－3π/8，kπ/2－π/8)，其中k∈Z 最小正周期是π/2=π/2
kπ-π/2<2x+π/4(kπ)/2-3π/8定义域是:(kπ/2-3π/8，kπ/2-π/8)，其中k∈Z最小正周期是π/2=π/2
