Help with Core 3 Level Trigonometry Question

[CathyLou]

Hi.

Could someone please explain to me the following C3 level trigonometry question? I would really appreciate any help as I am completely stuck at the moment.

Express tan2x/(1 - ((tan^2)2x)) in a more simple form.

The answer in the back of the textbook is (1/2)tan4x.

Thank you.

Cathy

 

[rock.freak667]

remember that $$tan2A=\frac{2tanA}{1-tan^2A}$$

does what you have look similar to that form?