1. ## Trig function q

If cos A = 3/5, express cos^2 A - sin^2 A in the form p/q.
I've found sin = 4/5 but I know how to express it into cos^2A and all.
Can someone help me please? Thanks!

2. Originally Posted by Detanon
If cos A = 3/5, express cos^2 A - sin^2 A in the form p/q.
I've found sin = 4/5 but I know how to express it into cos^2A and all.
Can someone help me please? Thanks!
But all that remains now is fraction computation...

cos A = 3/5, sin A = 4/5. So cos^2 A = 9/25, sin^2 A= 16/25 and so on...