IMO 2023 Shortlist G7
Let ABC be an acute, scalene triangle with orthocentre H. Let a be the line through the reflection of B with respect to ...
Category: Geometry
Problem
Let ABC be an acute, scalene triangle with orthocentre H. Let a be the line through the reflection of B with respect to CH and the reflection of C with respect to BH. Lines b
and c are defined similarly. Suppose lines a, b, and c determine a triangle T .
Prove that the orthocentre of T , the circumcentre of T and H are collinear.
(Ukraine)