r155	point X(56), perspective
r156	circumcenter, incenter,point X(57), radical center
r973	perspective, circumcircle, isogonal points, anticomplement, Nagel point
r1805	incenter, point X(57), circumcircle
r1812	concyclic points
r1833	isogonal points, incenter, point X(56), circumcircle, Spieker point
r1834	incenter, circumcircle, inverse points