大题我来给你做：1f(x)=a·b=(sinx/2,sqrt(3)cosx/2)·(cosx/2,cosx/2)=(1/2)sinx+(sqrt(3)/2)cosx+sqrt(3)/2=sin(x+π/3)+sqrt(3)/2,f(x)=0,则：sin(x+π/3)=-sqrt(3)/2,即：x+π/3=2kπ-π/3或x+π/3=2kπ-2π/3,...