Show that there exists a triangle
Source:
September 14, 2010
combinatorics unsolvedcombinatorics
Problem Statement
Let and be two finite disjoint sets of points in the plane such that no three distinct
points in are collinear. Assume that at least one of the sets contains at least five points. Show that there exists a triangle all of whose vertices are contained in or in that does not contain in its interior any point from the other set.