Point
lies on side
of a convex quadrilateral
. Let
be the incircle of triangle
, and let
be its incenter. Suppose that
is tangent to the incircles of triangles
and
at points
and
, respectively. Let lines
and
meet at
, and let lines
and
meet at
. Prove that points
,
, and
are collinear.
Author: Waldemar Pompe, Poland
%V0
Point $P$ lies on side $AB$ of a convex quadrilateral $ABCD$. Let $\omega$ be the incircle of triangle $CPD$, and let $I$ be its incenter. Suppose that $\omega$ is tangent to the incircles of triangles $APD$ and $BPC$ at points $K$ and $L$, respectively. Let lines $AC$ and $BD$ meet at $E$, and let lines $AK$ and $BL$ meet at $F$. Prove that points $E$, $I$, and $F$ are collinear.
Author: Waldemar Pompe, Poland