In Euclidean geometry, Kosnita's theorem is a property of certain circles associated with an arbitrary triangle. Let △ABC be an arbitrary triangle, O its circumcenter and Oa, Ob, Oc are the circumcenters of three triangles △OBC, △OCA, and △OAB respectively. The theorem asserts that the three straight lines AOa, BOb, and COc are concurrent. This result was established by the Romanian mathematician Cezar Coşniţă (1910–1962). Their point of concurrence is known as the triangle's Kosnita point (named by Rigby in 1997). It is the isogonal conjugate of the nine-point center. It is triangle center X(54) in Clark Kimberling's list.
References