Show that [itex]\displaystyle{\sum_{k=1}^{n-1}\sin\frac{km\pi}{n}\cot\frac{k\pi}{2n} = n-m}\quad\quad(m,n\in\mathbb{N}^+,\ m\le n)[/itex](adsbygoogle = window.adsbygoogle || []).push({});

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# A trig identity [tough]

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