Youtube videos by Julie Harland are organized at http://YourMathGal.com. We verify a Trig identity by using the basic identities and the identity for the cosine of a sum or difference. We prove that (cos(x+y))/(cosx·cosy) = 1 - tanx·tany using a trig proof.
Thank you so much for this video! It really helped me a lot! You explain things very nicely and you don't sound annoyed!
yomaster29 3 months ago