Question

1)2+sin^2a+cos^2a
2) sina cos^2a+sin^3a
3) (1-sina)(1+sina)

Answer 1

$2+sin^2a+cos^2a=3\sinacos^2a+sin^3=sina(cos^2a+sin^2a)=sina\(1-sina)(1+sina)=1-sin^2a=cos^2a$