MathDB
combo geo with arcs

Source: 2007 Swedish Mathematical Competition p4

April 27, 2021
geometrycombinatorial geometryarcs

Problem Statement

There are a number of arcs on the edge of a circular disk. Each pair of arcs has the least one point in common. Show that on the circle you can choose two diametrical opposites points such that each arc contains at least one of these two points.