sinx单调增区间 2kπ-π/2 ≤ x ≤ 2kπ+π/2令2kπ-π/2 ≤ π/4-2x ≤ 2kπ+π/2,可求y的单调增区间.[kπ-π/8,kπ+3π/8]sinx单调减区间 2kπ+π/2 ≤ x ≤ 2kπ+3π/2令2kπ+π/2 ≤ π/4-2x≤ 2kπ+3π/2,可求...