公式：2sinAcosB = sin(A+B) +sin(A-B)
f(x)=2cosxsin(x+π/3)-√3/2 = sin(x+π/3+x) + sin(x+π/3-x) - √3/2
= sin(2x+π/3) + √3/2 - √3/2
= sin(2x+π/3)
最小正周期：2π/2 = π