MathDB
triangle with vertices at three of the given points

Source: IMO Shortlist 2004, number theory problem 7

June 14, 2005
analytic geometryTrianglecoordinate geometryDivisibilityIMO Shortlist

Problem Statement

Let pp be an odd prime and nn a positive integer. In the coordinate plane, eight distinct points with integer coordinates lie on a circle with diameter of length pnp^{n}. Prove that there exists a triangle with vertices at three of the given points such that the squares of its side lengths are integers divisible by pn+1p^{n+1}.
Proposed by Alexander Ivanov, Bulgaria