=根号2(根号2/2*sin2x + 根号2/2*cos2x)
=根号2sin(2x +π/4 )
π/2+2kπ≤2x+π/4≤3π/2+2kπ
π/4+2kπ≤2x≤5π/4+2kπ
π/8+kπ≤x≤5π/8+kπ
[π/8+kπ,5π/8+kπ]
为单调递减区间
=根号2(根号2/2*sin2x + 根号2/2*cos2x)
=根号2sin(2x +π/4 )
π/2+2kπ≤2x+π/4≤3π/2+2kπ
π/4+2kπ≤2x≤5π/4+2kπ
π/8+kπ≤x≤5π/8+kπ
[π/8+kπ,5π/8+kπ]
为单调递减区间