解:cos(π/3-α)=cos[π/2-(π/6+α)]=sin(π/6+α)(诱导公式)=√3/3
cos(π/3-α)= cos(α- π/3 )=cos(α+π/6-π/2)=sin( α+π/6)=√3/3
π/2-(π/6+a)=(π/3-a)所以结果等于正负三分之根号三