# Trigonometry (2)

Geometry Level 4

$\large S_n= \cos^2 \dfrac{π}{n} + \cos^2 \dfrac{2π}{n} + \cos^2 \dfrac{3π}{n} + \cdots + \cos^2 \dfrac{(n-1)π}{n}$

For integer $n\geq 2$, simplify $S_n$ to an algebraic function of $n$.

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