The point Ko of concurrence in Kosnita theorem, i.e., the point of concurrence of the lines connecting the vertices , ,
and of a triangle with the circumcenters of the
triangles ,
, and (where is the circumcenter of ). The point was so named by Rigby
(1997), and is the isogonal conjugate of the
nine-point center (Grinberg 2003).
de Villiers, M. "A Dual to Kosnita's Theorem." Math. and Informatics Quart.6, 169-171, 1996. http://mzone.mweb.co.za/residents/profmd/kosnita.htm.Grinberg,
D. "On the Kosnita Point and the Reflection Triangle." Forum Geom.3,
105-111, 2003. http://forumgeom.fau.edu/FG2003volume3/FG200311index.html.Kimberling,
C. "Triangle Centers and Central Triangles." Congr. Numer.129,
1-295, 1998.Kimberling, C. "Encyclopedia of Triangle Centers: X(54)=Kosnita
Point." http://faculty.evansville.edu/ck6/encyclopedia/ETC.html#X54.Musselman,
J. R. and Goormaghtigh, R. "Advanced Problem 3928." Amer. Math.
Monthly46, 601, 1939.Musselman, J. R. and Goormaghtigh,
R. "Solution to Advanced Problem 3928." Amer. Math. Monthly48,
281-283, 1941.Rigby, J. "Brief Notes on Some Forgotten Geometrical
Theorems." Math. and Informatics Quart.7, 156-158, 1997.
, 
,
and 
of a triangle 
with the circumcenters of the
triangles 
,
, and 
(where 
is the circumcenter of 
). The point was so named by Rigby
(1997), and is the isogonal conjugate of the
nine-point center (Grinberg 2003).
(Kimberling 1998, p. 75; note spelling correction).
