Question 58
Evaluate the sums
$$
\sum_{k=1,\ k \neq r}^{n} \cot \left( \frac{(k-r)\pi}{n+1} \right), \quad r = 1, 2, \dots, n.
$$
$$
\sum_{k=1,\ k \neq r}^{n} \cot \left( \frac{(k-r)\pi}{n+1} \right), \quad r = 1, 2, \dots, n.
$$
MathNet 2026 — Part 06 Question 58
Math Olympiad Vault · MathNet 2026 — Part 06