IMO Shortlist 2011 problem G7
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Avg: 9,0 Let
be a convex hexagon all of whose sides are tangent to a circle
with centre
. Suppose that the circumcircle of triangle
is concentric with
. Let
be the foot of the perpendicular from
to
. Suppose that the perpendicular from
to
intersects the line
at a point
. Let
be the foot of the perpendicular from
to
. Prove that
.
Proposed by Japan
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Proposed by Japan
Izvor: Međunarodna matematička olimpijada, shortlist 2011