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 be an odd prime and a positive integer. In the coordinate plane, eight distinct points with integer coordinates lie on a circle with diameter of length . 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 .Proposed by Alexander Ivanov, Bulgaria