IMO 1972 LL CZS9

Given natural numbers k and n, k \leqn, n \geq3, find the set

imolonglistmathematicsolympiad

IMO 1972 LL CZS9

Origin: CZS

Problem

Given natural numbers k and n, k \leqn, n \geq3, find the set of all values in the interval (0, \pi) that the kth-largest among the interior angles of a convex ngon can take.