1. What two common identities are most useful for simplifying 2tanx/(sin^2x + cos^2x - tan^2x)?

Question

Two identities are: sin^2x + cos^2x = 1 and tan2x=2tanx/1-tan^2x

Answer 1

your are correct

2tanx/(sin^2x + cos^2x - tan^2x)
= 2tanx/(1 - tan^2 x)
= tan(2x)

Answer 2

Thank you~