IMO Shortlist 2011 problem G1


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23. lipnja 2013.
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Let ABC be an acute triangle. Let \omega be a circle whose centre L lies on the side BC. Suppose that \omega is tangent to AB at B' and AC at C'. Suppose also that the circumcentre O of triangle ABC lies on the shorter arc B'C' of \omega. Prove that the circumcircle of ABC and \omega meet at two points.

Proposed by Härmel Nestra, Estonia
Izvor: Međunarodna matematička olimpijada, shortlist 2011