MathDB

2

Part of 2024 Austrian MO Regional Competition

Problems(1)

orthocenter of ABC is circumcenter of APQ

Source: 2024 Austrian Regional Competition For Advanced Students p2

3/26/2024
Let ABCABC be an acute triangle with orthocenter HH. The circumcircle of the triangle BHCBHC intersects ACAC a second time in point PP and ABAB a second time in point QQ. Prove that HH is the circumcenter of the triangle APQAPQ.
(Karl Czakler)
geometrycircumcircle