Вычислите cos^2150°-(sin70°*cos40°-cos70°*cos50°)^2

Question

Вычислите cos^2150°-(sin70°*cos40°-cos70°*cos50°)^2

Answer 1

Cos(2160-10)*(sin70°*cos40°-cos70°*cos(90-40))²=cos10*(sin70°*cos40°-cos70°*sin40)²=
=cos10*sin²(70-40)=cos10*sin²30=1/4 cos10