# Pre-Calculus

posted by
**Corin** on
.

How can the following two identities be verified?

1. (cos^2y)/(1-siny)=1+siny

2. sin^2a-sin^4a=cos^2a-cos^4a

Thanks!

change cos^2a to 1-sin^2a=(1-sina)(1+sina)

Thank you. I figured out the first one with your help, but I'm still stuck on the second. Any tips?