f(x)=cos(x/4+π/3)sin(x/4-π/2)
=-cos(x/4+π/3)cos(x/4)
=-[cos(x/4)cos(π/3)-sin(x/4)six(π/3)]cos(x/4) （拆分）
=-[1/2cos(x/4)-√3/2sin(x/4)]cos(x/4) (把cos乘进去）
=-[1/2cos(x/4)cos(x/4)-√3/2sin(x/4)cos(x/4)]
=-[1/4cos(x/2)+1/4-√3/4sin(x/2)]
=√3/4sin(x/2)-1/4cos(x/2)-1/4 (去负号）
=1/2[√3/2sin(x/2)-1/2cos(x/2)]-1/4
=1/2[cos(π/6)sin(x/2)-sin(π/6)cos(x/2)]-1/4
=1/2sin(x/2-π/6)-1/4