The Spieker center is the center S p of the Spieker circle, i.e., the incenter of the medial triangle of a reference triangle Δ A B C. It is also the center of the excircles radical circle. It has equivalent triangle center functions α_10 | = | b c(b + c) α_10 | = | (b + c)/a, and is Kimberling center X_10. The Spieker center is also the centroid of the perimeter of the original triangle, as well as the cleavance center (Honsberger 1995; illustrated above).

Brocard points | cleavance center | cleaver | incenter | isotomic conjugate | Nagel line | perimeter | Spieker circle | Taylor center | triangle centroid