Question

Доказать равенство(тождество)
sin⁴ а + сos⁴a - sin⁶a - cos⁶a = (sin²2a) / 4

Answer 1

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