IMO Shortlist 2006 problem G7
Avg:
Avg:
In a triangle
, let
,
,
be the midpoints of the sides
,
,
, respectively, and
,
,
be the midpoints of the arcs
,
,
of the circumcircle of
, not containing the vertices
,
,
, respectively. For
, let
be the circle with
as diameter. Let
be the common external common tangent to the circles
and
(for all
) such that
lies on the opposite side of
than
and
do.
Prove that the lines
,
,
form a triangle similar to
and find the ratio of similitude.




























Prove that the lines




Izvor: Međunarodna matematička olimpijada, shortlist 2006