cos^2A+cos^2(A+60)-cosA*cos(A+60)=1/2(1+c0s2A)+1/2[1+cos(2A+120)]-cosA*(cosAcos60-sinAsin60)=1+1/2cos2A+1/2(cos2Acos120-sin2Asin120)-(cosA)^2cos60+1/2sin2Asin60=1+1/2cos2A-1/4cos2A-1/2sin2Asin120-1/2(...