IMO 1998 Problem 1
- Day 1
A convex quadrilateral has perpendicular diagonals. The perpendicular bisectors of the sides and meet at a unique point inside . Prove that the quadrilateral is cyclic if and only if triangles and have equal areas.
Attachments:

Dataset text AI-MO AoPS. Quoted with source.
Official text: IMO 1998 official English paper, page 1.
Solutions
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