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MathNet 2016-part-02 — 184 problems (EN–VI) Question 132

Math Olympiad Vault · MathNet 2016-part-02 — 184 problems (EN–VI)

Question 132

Let $ABC$ be a triangle with $AB \neq AC$. The points $K, L, M$ are the midpoints of the sides $BC, CA, AB$, respectively. The inscribed circle of $ABC$ with centre $I$ touches the side $BC$ at point $D$. The line $g$, which passes through the midpoint of segment $ID$ and is perpendicular to $IK$, intersects the line $LM$ at point $P$.

Prove that $\angle PIA = 90^{\circ}$.