2016 OIM Problems/Problem 5

Problem

The circles $\Gamma_1$ and $\Gamma_2$ intersect at two different points $A$ and $K$. The tangent common to $\Gamma_1$ and $\Gamma_2$ closest to $K$ touches $\Gamma_1$ at $B$ and $\Gamma_2$ at $C$. Let $P$ be the foot of the perpendicular from $B$ on $AC$, and $Q$ the foot of the perpendicular from $C$ on $AB$. If $E$ and $F$ are the symmetrical points of $K$ with respect to the lines $PQ$ and $BC$, prove that the points $A, E$ and $F$ are collinear.

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

Solution

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See also

OIM Problems and Solutions