Question

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

Answer 1

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