kπ+π/8≤x＜π/2或π/2＜x≤5π/8+kπ
2sin（2x-45度）≥0 kπ+π/8≤x≤5π/8+kπ
cosx≠0 x≠π/2
取交集后得 kπ+π/8≤x＜π/2或π/2＜x≤5π/8+kπ