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MathNet 2016-part-05 — 184 problems (EN–VI) Question 28

Math Olympiad Vault · MathNet 2016-part-05 — 184 problems (EN–VI)

Question 28

In $\triangle ABC$ ($AB \neq AC$) the incircle, with center $I$, touches the side $BC$ at $D$. Let $M$ be the midpoint of segment $BC$. Prove that the perpendiculars from $M$ to $AI$ and from $D$ to $MI$, respectively, meet on the line containing the altitude of $\triangle ABC$ from vertex $A$.

(Dusan Djukic)