set of 4 lines such one is parallel to a medina determined by other 3
Source: 1996 German Federal - Bundeswettbewerb Mathematik - BWM - Round 1 p3
January 27, 2020
combinatorial geometrygeometrymedian
Problem Statement
Four lines are given in a plane so that any three of them determine a triangle. One of these lines is parallel to a median in the triangle determined by the other three lines. Prove that each of the other three lines also has this property.