f(x)=sin(x)sin(x+π/2)-√3cos²（3π+x)+1/2√3 =sinxcosx-√3cos²x+1/2√3 =1/2sin2x-√3/2(2cos²x-1) =1/2sin2x-√3/2cos2x =sin(2x-π/3)固最小正周期为T=π
