f(x)=sin2x-(1-)2sinx^2=sin2x-cos2x
=√2sin(2x-π/4)
1. 最小正周T=2π/2=π
最大值=√22x-π/4=2kπ+π/2x=kπ+3π/8
2.单调减区间
2kπ+π/2