MathDB
Parallel bisectors -IMO Long List P2

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August 28, 2010
geometryangle bisectorgeometry proposed

Problem Statement

Let ABCDABCD be a convex quadrilateral. DADA and CBCB meet at FF and ABAB and DCDC meet at EE. The bisectors of the angles DFCDFC and AEDAED are perpendicular. Prove that these angle bisectors are parallel to the bisectors of the angles between the lines ACAC and BD.BD.
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