Erasing diagonals in an n-gon
Source: Kürschák 1994, problem 2
July 19, 2014
combinatorics unsolvedcombinatorics
Problem Statement
Prove that if we erase diagonals of a regular -gon, then we may still choose of the remaining diagonals such that they don't intersect inside the -gon; but it is possible to erase diagonals such that this statement doesn't hold.