Question

срочно
(sina + cosa)^2 + ( sina - cosa )^2

Answer 1

$(sina+cosa)^2+(sina-cosa)^2=\\=sin^2a+2sinacdot cosa+cos^2a+sin^2a-2sinacdot cosa+cos^2a=\\=(sin^2a+cos^2a)+(sin^2a+cos^2a)=1+1=2$