Question

How do you get from (1-tan^2(a/2))/(1/cos^2(a/2)) to cos^2(a/2)-cos^2(a/2)*tan^2(a/2) ? I've tried using different pythagorean identities for over an hour now, but I never get there.

Answer 1

This is your answer so simple just use 1/cos^2(a/2) and it will get multiplied to the numerator and open the bracket and you will the answer.