cos(2arctan根号6+π/3)=cos(2arctan根号6）cos(π/3)-sin(2arctan根号6)sin(π/3)={2cos^2(arctan根号6)-1}*1/2-2sin(arctan根号6）cos（arctan根号6）*1/2*根号3=cos^2(arctan根号6)-1/2-sin(arctan根号6）cos（ar...