# Thread: Double angle formula

1. ## Double angle formula

Is it possible to input $\displaystyle \frac{2\;tan\;\frac{\pi}{5}}{1-tan^2\;\frac{\pi}{5}}$ on a calculator? The $\displaystyle tan^2$ in the denominator is throwing me off.

2. Originally Posted by TI-84
Is it possible to input $\displaystyle \frac{2\;tan\;\frac{\pi}{5}}{1-tan^2\;\frac{\pi}{5}}$ on a calculator? The $\displaystyle tan^2$ in the denominator is throwing me off.
just enter $\displaystyle \left( \tan \frac {\pi}5 \right)^2$