Question

How do you verify (1+sinθ)(1−sinθ)=cos2θ?

Answer 1

(1+sin a)(1-sin a)=cos^2 a

(1)^2-(sin a)^2=cos^a

1-sin^2 a=cos^2 a

cos^2 a=cos^2 a(sin^2 a+cos ^2 a=1)