2020 OIM Problems/Problem 1

Problem

Let $ABC$ be an acute triangle such that $AB < AC$. The midpoints of sides $AB$ and $AC$ are $M$ and $N$, respectively. Let $P$ and $Q$ be points on the line $MN$ such that $\angle CBP = \angle ACB$ and $\angle QCB = \angle CBA$. The circumcircle of triangle $ABP$ intersects the line $AC$ in $D$ ($D \ne A$) and the circumcircle of the triangle $AQC$ intersects the line $AB$ in $E$ ($E \ne A$). Show that the lines $BC$, $DP$ and $EQ$ are concurrent.

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

Solution

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See also

OIM Problems and Solutions