Prove the Identity (trig identities)

[blitzen]

I have to prove the following:

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

I know that the numerator, (1 + tan^2 u) is equivalent to sec^2 u, but I do not know where to go from there.

 

[Deleted member 4993]

I have to prove the following:

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

I know that the numerator, (1 + tan^2 u) is equivalent to sec^2 u, but I do not know where to go from there.

Then multiply the numerator and the denominator by cos[sup:suzxj04u]2[/sup:suzxj04u](u)

OR

Start by converting

tan(u) = sin(u)/cos(u)