1. The problem statement, all variables and given/known data Teacher gave this identity twice to us but the starting position slightly varies. Prove sec(2x) - tan(2x) = (cos(x)-sin(x))/(cos(x) + sin(x)) Prove cos(2x)/(1 + sin(2x)) = tan(pi/4-x) 2. Relevant equations pretty much all trig identities 3. The attempt at a solution I get to (1-sin(2x))/cos(2x) = (cos(x)-sin(x))/(cos(x) + sin(x)) and then I'm stumped.