I need help with Trigonometrics identies

[Shannonwat]

Hi, I am having some problems with trigonometric identities. I have looked over the problems and I know that can work either side but do you have any other hints....

Ex. (1 + sinx)(1 - sinx) = cos2x

 

[stapel]

What have you tried? You've multiplied out the left-hand side, applied the Pythagorean Identity, and... then what?

By the way, if the right-hand side is "cos(2x)", as you have posted, then the equation isn't an identity. Were you supposed to solve this equation...?

Thank you.

Eliz.