Question

in the one you helped me with, where did this come from: Where did this part come from?
- (sin^2Ø + cos^2Ø)

Answer 1

you should have come across the identity
sin^2Ø + cos^2Ø = 1 , called the Pythagorean

so I replaced 1 with that expression

Answer 2

oh. I didn't think to connect it with that. Thank you for pointing it out to me.