(sin2a+3cos2a)^2 + (cos2a-3sin 2a)^2

Question

(sin2a+3cos2a)^2 + (cos2a-3sin 2a)^2

Answer 1

Sin²2a+6sin2acos2a+9cos²2a+cos²2a-6cos2asin2a+9sin²a=
=10sin²2a+10cos²2a=10(sin²2a+cos²2a)=10*1=10