Problem
COM-B2-M06-P002 Two Sides of One Colour
#2
★★☆☆☆ Level 2 of 5
The edges of a triangle are coloured red and blue. Prove that two of its sides have the same colour.
Three edges are distributed between two colours.
A triangle has \(3\) edges and only \(2\) colours. By the pigeonhole principle, two edges have the same colour.
This is not a monochromatic triangle, but it is a useful warm-up.