# Math Help - cosinus

1. ## cosinus

Hi,

How to show that $(cos(\frac{\pi}{2^{n+1}}))^2 > cos(\frac{\pi}{2^n})$???

2. $\cos 2a = 2\cos^2 a -1$

$\cos \frac{\pi }{2^n} = \cos 2\frac{\pi}{2^{n+1}}$

$-1 \leq \cos a \leq 1$

can you solve it now with these hints