2 colors for 6 points
Source: Polish MO second round 1966 p3
August 28, 2024
geometryColoringcombinatorial geometrycombinatorics
Problem Statement
points are selected on the plane, none of which lie on one straight line, and all pairwise segments connecting these points are plotted. Some of the sections are plotted in red and others in blue. Prove that any three of the given points are the vertices of a triangle with sides of the same color.