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TOT 340 1992 Autumn O J2 circumcenters are vertices of #

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June 10, 2024
geometryparallelogramcircumcircle

Problem Statement

On each side of a parallelogram an arbitrary point is chosen. Each pair of chosen points on neighbouring sides (i.e. sides with a common vertex) are connected by a line segment. Prove that the centres of the circumscribed circles of the four triangles so created are themselves vertices of a parallelogram.
(ED Kulanin)