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IMO 2019 — Complete Shortlist Question 18

IMO Shortlist · IMO 2019 — Complete Shortlist

Question 18

Let $A B C$ be an acute-angled triangle and let $D, E$, and $F$ be the feet of altitudes

from $A, B$, and $C$ to sides $B C, C A$, and $A B$, respectively. Denote by $\omega_{B}$ and $\omega_{C}$ the incircles of triangles $B D F$ and $C D E$, and let these circles be tangent to segments $D F$ and $D E$ at $M$ and $N$, respectively. Let line $M N$ meet circles $\omega_{B}$ and $\omega_{C}$ again at $P \neq M$ and $Q \neq N$, respectively. Prove that $M P=N Q$.