MathDB
placing lightbulbs around n-gon to light it up

Source: Bulgaria 1986 P4

June 15, 2021
geometrycombinatoricscombinatorial geometry

Problem Statement

Find the smallest integer n3n\ge3 for which there exists an nn-gon and a point within it such that, if a light bulb is placed at that point, on each side of the polygon there will be a point that is not lightened. Show that for this smallest value of nn there always exist two points within the nn-gon such that the bulbs placed at these points will lighten up the whole perimeter of the nn-gon.