MathDB
2018 PAMO Shortlist: Circle with diameter AC, angle bisector, midsegment concur

Source: 2018 Pan-African Shortlist - G1

May 6, 2019
geometryangle bisector

Problem Statement

In a triangle ABCABC, let DD and EE be the midpoints of ABAB and ACAC, respectively, and let FF be the foot of the altitude through AA. Show that the line DEDE, the angle bisector of ACB\angle ACB and the circumcircle of ACFACF pass through a common point.
Alternate version: In a triangle ABCABC, let DD and EE be the midpoints of ABAB and ACAC, respectively. The line DEDE and the angle bisector of ACB\angle ACB meet at GG. Show that AGC\angle AGC is a right angle.