The point Ko of concurrence in Kosnita theorem, i.e., the point of concurrence of the lines connecting the vertices A, B, and C of a triangle Δ A B C with the circumcenters of the triangles Δ B C O, Δ C A O, and Δ A B O (where O is the circumcenter of Δ A B C). The point was so named by Rigby, and is the isogonal conjugate of the nine-point center. The Kosnita point has triangle center function α = sec(B - C) and is Kimberling center X_54 (Kimberling 1998, p. 75; note spelling correction).

Kosnita theorem | triangulation point