MathDB

Let a non-isosceles acute triangle ABC with the circumscribed cycle (O) and the orthocenter H. D, E, F are the reflection of O in the lines BC, CA and AB. a)

H_a

is the reflection of H in BC, A' is the reflection of A at O and

O_a

is the center of (BOC). Prove that

H_aD

and OA' intersect on (O). b) Let X is a point satisfy AXDA' is a parallelogram. Prove that (AHX), (ABF), (ACE) have a comom point different than A

Problem Statement