Question

Помогите пожалуйста !3

Answer 1

$sin^6a+cos^6a+frac{3}{4}sin^22a=\\=(underbrace {sin^2a+cos^2a}_{1})(sin^4a-sin^2acdot cos^2a+cos^4a)+frac{3}{4}sin^22a=\\=sin^4a-sin^2acdot cos^2a+cos^4a+frac{3}{4}(underbrace {2sinacdot cosa}_{sin2a})^2=\\=sin^4a-sin^2acdot cos^2a+cos^4a+ frac{3}{4}cdot 4sin^2acdot cos^2a=\\=sin^4a+2sin^2acdot cos^2a+cos^4a=\\=(sin^2a+cos^2a)^2=1^2=1$