Question

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

Answer 1

Вроде вот так будет...
(sina+cos)^2+(sina-cosa)^2=
=(sin^2a+2sinacosa+cos^a)+(sin^2a-2sinacosa+cosa)=
=2sin^2a+2cos^2a=2 

Answer 2

$(sin a+cosa)^2+(sin a-cos a)^2=\\sin^2 a-2sin acosa+cos^2 a+sin^2 a-2sin acos a+cos^2 a=\\2(sin^2 a+cos^2 a)=2*1=2$