2010.D3

Part of Durer Math Competition CD 1st Round - geometry

Problems(1)

quad is orthodiagonal if midpoints are concyclic 2009-10 Dürer Round1 D3

Source:

Prove that the diagonals of a quadrilateral are perpendicular to each other if and only if the midpoints of it's sides lie on a circle.

geometryConcyclicdure