MathDB
Determine angle C

Source: I.F.Sharygin contest 2009 - Correspondence round - Problem 10

May 31, 2009
geometrycircumcircletrapezoidperpendicular bisectorgeometry proposed

Problem Statement

Let ABC ABC be an acute triangle, CC1 CC_1 its bisector, O O its circumcenter. The perpendicular from C C to AB AB meets line OC1 OC_1 in a point lying on the circumcircle of AOB AOB. Determine angle C C.
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