MathDB
Partition a (4n-1)-gon

Source: Romania TST 1 P4, 2013

April 5, 2013
combinatorics unsolvedcombinatorics

Problem Statement

Let nn be an integer greater than 1. The set SS of all diagonals of a (4n1) \left( 4n-1\right) -gon is partitioned into kk sets, S1,S2,,Sk,S_{1},S_{2},\ldots ,S_{k}, so that, for every pair of distinct indices ii and j,j, some diagonal in SiS_{i} crosses some diagonal in Sj;S_{j}; that is, the two diagonals share an interior point. Determine the largest possible value of kk in terms of n.n.