# Trigo Series

Geometry Level 4

$\cos \left( \frac{\pi}{2n+1} \right) + \cos \left( \frac{3\pi}{2n+1} \right) + \cos \left( \frac{5\pi}{2n+1} \right) +\cdots$

Find the sum of the above expression up to $$n$$ terms.

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