The Steiner circumellipse is the circumellipse that is the isotomic conjugate of the line at infinity and the isogonal conjugate of the Lemoine axis. It has circumconic parameters x:y:z = 1/a :1/b :1/c, giving trilinear equation 1/(a α) + 1/(b β) + 1/(c γ) = 0 (Vandeghen 1965; Kimberling 1998, p. 236). The Steiner circumellipse is often simply called the "Steiner ellipse, " but the designation "circumellipse" is useful to distinguish it from the less important curve known as the Steiner inellipse.

bickart points | isotomic conjugate | line at infinity | Steiner inellipse | Thomsen's figure

Jakob Steiner