Question

Докажите тождество: sin^4a+cos^4a-sin^6a-cos^6a=sin^2a*cos^2a

Answer 1

sin^4a(1-sin²a)+cos^4a(1-cos²a)=sin^4a*cos²a+cos^4a*sin²a)=
=sin²acos²a(sin²a+cos²a)=sin²acos²a