MathDB
Cyclic quads and collinear points

Source: 2021 Nigerian MO Round 3/P2

December 19, 2022
geometryCyclic Quadrilaterals

Problem Statement

Let B,C,D,EB, C, D, E be four pairwise distinct collinear points and let AA be a point not on ine BCBC. Now, let the circumcircle of △ABC\triangle ABC meet ADAD and AEAE respectively again at FF and GG. Show that DEFGDEFG is cyclic if and only if AB=ACAB=AC.
Back to ProblemsView on AoPS