# Math Help - Find tan3x in terms of tanx.

1. ## Find tan3x in terms of tanx.

Find tan3x in terms of tanx.

Not sure where my starting point is?

Thanks.

2. Start with the formula for $tan(a+ b)= \frac{tan(a)+ tan(b)}{1+ tan(a)tan(b)}$. Use that to find a formula for tan(2x) and then use tan(3x)= tan(2x+ x).