4
$\begingroup$

Possible Duplicate:
Sum of the reciprocal of sine squared

Can anyone help me?

If $\alpha=\frac{\pi}{N}$, where $N\geqslant 2$

How to prove the following equation?

$\sum_{k=1}^{N-1}\frac1{\sin^2(k\alpha)}=\frac{N^2-1}{3}$

  • 0
    Good eye, @Sam!2012-05-03

0 Answers 0