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MathNet 2022-part-01 — 197 problems (EN–VI) Question 44

Math Olympiad Vault · MathNet 2022-part-01 — 197 problems (EN–VI)

Question 44

Let $ABC$ be a triangle with circumcircle $\omega$, circumcenter $O$, and orthocenter $H$. Let $K$ be the midpoint of $AH$. The perpendicular to $OK$ at $K$ intersects $AB$ and $AC$ at $P$ and $Q$, respectively. The lines $BK$ and $CK$ intersect $\omega$ again at $X$ and $Y$, respectively. Prove that the second intersection of the circumcircles of triangles $KPY$ and $KQX$ lies on $\omega$.