Homework Statement
Show that the exact value of tan°43' is \frac{\sqrt{5}-1}{2}
Homework Equations
The Attempt at a Solution
tan2x = \frac{2tanx}{1-tan^{2}x}
\frac{2tan31° 43}{1-tan^{2}31° 43'}
From here, i got stuck or I'm doing it wrongly, i forgot how to do it...