Question

Докажите тождество:
(sinb+sina)(sina-sinb)-(cosa+cosb)(cosb-cosa)=0

Answer 1

sin^2 a-sin^2b-cos^2b+cos^2a=0;
(sin^2 a+cos^2 a)-(sin^2b+cos^2 b)=0;
1-1=0;
0=0