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MathNet 2023-part-02 — 191 problems (EN–VI) Question 8

Math Olympiad Vault · MathNet 2023-part-02 — 191 problems (EN–VI)

Question 8

We are given an acute triangle $A B C$. Let $D$ be the point on its circumcircle such that $A D$ is a diameter. Suppose that points $K$ and $L$ lie on segments $A B$ and $A C$, respectively, and that $D K$ and $D L$ are tangent to circle $A K L$.
Show that line $K L$ passes through the orthocentre of $A B C$.
The altitudes of a triangle meet at its orthocentre.

Question illustration