f(x)=sin(x/3)cos(x/3)+(根号3)cos^2(x/3)
=1/2sin(2x/3)+（根号）3*[cos(2x）/3+1]/2
=cos(π/3)sin(2x/3)+sin(π/3)cos(2x/3)+根号3/2
=sin[(2x+π)/3]+根号3/2