The Feuerbach Conic Theorem

FeuerbachConic:=proc() local A,B,C,H,C1,c,d:

H:=Orthocenter(A,B,C):   C1:=Center( ConicThroughPoints ([A,B,C,H])):

PtLiesOnCurve (C1   ,   NinePointCircle (A,B,C)):

end: