Eckart Schmidt, Circumcenters of Residual Triangles,
Forum Geometricorum 3 (2003) 207--214.

Abstract:  This paper is an extension of Mario Dalcín's work on isotomic inscribed triangles and their residuals [Forum Geom., 3 (2003) 125--134]. Considering the circumcircles of residual triangles with respect to isotomic inscribed triangles there are two congruent triangles of  circumcenters. We show that there is a rotation mapping these triangles to each other. The Center and angle of rotation depend on the Miquel points.  Furthermore we give an interesting generalization of Dalcín's definitive example.

[ps file] [pdf file]