2008 OIM Problems/Problem 2

Problem

Let $ABC$ be a scalene triangle and $r$ be the external bisector of the angle $\angle ABC$. $P$ and $Q$ are considered the feet of the perpendiculars to the line $r$ that pass through $A$ and $C$ respectively. Lines $CP$ and $AB$ intersect at $M$ and lines $AQ$ and $BC$ intersect at $N$. Show that the lines $AC, MN$ and $r$ have a point in common.

~translated into English by Tomas Diaz. ~orders@tomasdiaz.com

Solution

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See also

OIM Problems and Solutions