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MathNet 2018-part-01 — 181 problems (EN–VI) Question 145

Math Olympiad Vault · MathNet 2018-part-01 — 181 problems (EN–VI)

Question 145

Let $A B C$ be a triangle with orthocentre $H$, and let $D, E$, and $F$ denote the respective midpoints of line segments $A B, A C$, and $A H$. The reflections of $B$ and $C$ in $F$ are $P$ and $Q$, respectively.

a. Show that lines $P E$ and $Q D$ intersect on the circumcircle of triangle $A B C$.

b. Prove that lines $P D$ and $Q E$ intersect on line segment $A H$.