# Core 3 level help

1. Nov 2, 2007

### 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

2. Nov 2, 2007

### rock.freak667

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

does what you have look similar to that form?