函数f(x)=-√2(sin2x+π/4)+6 sin x cos x-2cos²x+1
1个回答

f(x)=-√2sin(2x+π/4)+6sinxcosx-2cos²x+1

=-√2(sin2xcosπ/4+cos2xsinπ/4)+3sin2x-2×(1+cos2x)/2+1

=-√2(√2/2·sin2x+√2/2·cos2x)+3sin2x-cos2x

=-sin2x-cos2x+3sin2x-cos2x

=2sin2x-2cos2x

=√[2²+(-2)²]sin(2x-π/4)

=2√2sin(2x-π/4)

1)最小正周期=2π/2=π

2)-π/2+2kπ≤2x-π/4≤π/2+2kπ k属于Z

-π/8+kπ≤x≤3π/8+kπ

递增区间[-π/8+kπ,3π/8+kπ]

∴f(x)在区间[0,π/2]上最大值为f(3π/8)=2√2,最小值为f(0)=-2