## anonymous one year ago Trigonometric expression help (look in comments)

1. anonymous

$\frac{ \tan 15 ° }{ 1 - \tan^215 ° }$ I know there's a formula but the answer in the back of my textbook gives me the solution: |dw:1443639097573:dw| How do you get the 1/2 and then the nominator is 2tan 15 °?

2. anonymous

the formula for tangent in this case (where there is $\tan 2\alpha$ ) is $\frac{ 2\tan \alpha }{ 1 - \tan^2 \alpha }$