IMO Shortlist 2007 problem G8
Avg:
Avg:
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




















Author: Waldemar Pompe, Poland
Izvor: Međunarodna matematička olimpijada, shortlist 2007