The reflection of the Orthocenter about the Circumcenter. This point is also the Orthocenter of the
Anticomplementary Triangle. It has Triangle Center Function
References
Altshiller-Court, N. ``On the de Longchamps Circle of the Triangle.'' Amer. Math. Monthly 33, 368-375, 1926.
Kimberling, C. ``Central Points and Central Lines in the Plane of a Triangle.'' Math. Mag. 67, 163-187, 1994.
Vandeghen, A. ``Soddy's Circles and the de Longchamps Point of a Triangle.'' Amer. Math. Monthly 71, 176-179, 1964.