MathDB
TOT 042 1983 Spring S-O5 sum of lengths by projections in regular polygon

Source:

August 18, 2019
combinatorial geometrycombinatoricscumprojectionregular polygon

Problem Statement

A point is chosen inside a regular kk-gon in such a way that its orthogonal projections on to the sides all meet the respective sides at interior points. These points divide the sides into 2k2k segments. Let these segments be enumerated consecutively by the numbers 1,2,3,...,2k1,2, 3, ... ,2k. Prove that the sum of the lengths of the segments having even numbers equals the sum of the segments having odd numbers.
(A Andjans, Riga)