f(x) = cos(x/2) = √3 sin(x/2) cos(x/2) + cos^2(x/2)= √3/2 sinx + 1/2(cosx+1)= √3/2 sinx + 1/2 cosx + 1= sinxcos(π/6) + cosxsin(π/6) + 1= sin(x+π/6) + 1最小正周期=2π/1=2π2kπ-π/2≤x+π/6＜2kπ...