# Math Help - Trig Questions !!

1. ## Trig Questions !!

Just gonna use " / " for divided by:

Express sin2A / 1 - cos 2A in terms of tanA only.

Express cos 2A - cos(squared)A / 1 + cos2A

any help at all would be much appreciated !! = )

2. Hi,

You might find the following identities useful:

sin(2x)=2sin(x)cos(x)
cos(2x)=cos^2(x)-sin^2(x)

And, of course, tan(x)=sin(x)/cos(x).

If you use these identities you should be on your way...

3. $\frac{\sin 2A}{1-\cos 2A}$

$=\frac{2\sin A \cos A}{2 \sin^2 A}$

$=\frac{1}{\tan A}$

use,

$\boxed { \sin 2A =2 \sin A . \cos A = \frac{2 \tan A}{1 + \tan^2 A}}$

$\boxed { \cos 2A = \cos^2 A - \sin^2 A = 2\cos^2 A - 1 = 1 - 2 \sin^2 A = \frac{1-\tan^2 A}{1+\tan^2 A}}$