y=sinx+cosx=√2[√2sinx/2+√2cosx/2]=√2sin(x+π/4)下面求单调递增区间2kπ-π/2 ≤x+π/4 ≤ 2kπ+π/22kπ-3π/4 ≤x≤ 2kπ+π/4单调递增区间[2kπ-3π/4 ,2kπ+π/4]下面求单调递减区间2kπ+π/2 ≤x+π/4 ≤...