MathDB

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Part of 2003 Iran MO (3rd Round)

Problems(1)

quadrilateral ....

Source: Iran(2003)

3/13/2004
assume ABCD a convex quadrilatral. P and Q are on BC and DC respectively such that angle BAP= angle DAQ .prove that [ADQ]=[ABP] ([ABC] means its area ) iff the line which crosses through the orthocenters of these traingles , is perpendicular to AC.
geometrygeometry solved