Stuck on all of these and can't see to get my answers anywhere close to the answers

a) Express $\displaystyle \frac{\sin2x}{1 - 2\cos2x}$ in terms of $\displaystyle \tan(x)$

b) Prove the identity $\displaystyle \frac{1 + \sin2A - \cos2A}{1 + \sin2A + \cos2A} \equiv \tan(A) $

and finally

c) Given that $\displaystyle \cos2A = \tan^{2}x$ show that $\displaystyle \cos2x = \tan^{2}A$