MathDB
incircle of a quadrilateral

Source: Indonesia IMO 2007 TST, Stage 2, Test 5, Problem 1

November 15, 2009
geometrycircumcirclecyclic quadrilateralangle bisectorgeometry proposed

Problem Statement

Let ABCD ABCD be a cyclic quadrilateral and O O be the intersection of diagonal AC AC and BD BD. The circumcircles of triangle ABO ABO and the triangle CDO CDO intersect at K K. Let L L be a point such that the triangle BLC BLC is similar to AKD AKD (in that order). Prove that if BLCK BLCK is a convex quadrilateral, then it has an incircle.
Back to ProblemsView on AoPS