MathDB
Menelaus theorem

Source: Nigeria Olympiad senior mathematics round 2 2020 problem 2

January 19, 2020
geometry

Problem Statement

Let DD be a point in the interior of ABCABC. Let BDBD and ACAC intersect at EE while CDCD and ABAB intersect at FF. Let EFEF intersect BCBC at GG. Let HH be an arbitrary point on ADAD. Let HFHF and BDBD intersect at II. Let HEHE and CDCD intersect at JJ . prove that GG,II and JJ are collinear