Y=(1-2cosx)(cosx)^2=2(sinx)^2*(cosx)^2=2(sinxcosx)^2=2(0.5sin2x)^2=0.5(sin2x)^2
而sin2x取值为（-1,1）故原式最大值为Y=0.5*1=0.5谢谢！周期呢？π/2