MathDB
MMO 015 Moscow MO 1935 concurrency in space

Source:

July 17, 2019
geometryconcurrent3D geometryparallel

Problem Statement

Triangles △ABC\vartriangle ABC and △A1B1C1\vartriangle A_1B_1C_1 lie on different planes. Line ABAB intersects line A1B1A_1B_1, line BCBC intersects line B1C1B_1C_1 and line CACA intersects line C1A1C_1A_1. Prove that either the three lines AA1,BB1,CC1AA_1, BB_1, CC_1 meet at one point or that they are all parallel.
Back to ProblemsView on AoPS