17th ibmo - el salvador 2002./q2
Source: Spanish Communities
April 14, 2006
modular arithmeticinvariantgeometrygeometric transformationreflectioncalculusintegration
Problem Statement
Given any set of points in the plane such that there is no of them collinear, show that for each point of the set, the number of triangles with its vertices on the other points and that contain on its interior is even.