I think that in general we have: Let 123456 be a hexagon whose the diagonals 14,25,36 concur at a point 0. For any point P the circuumcircles of P14, P25, P36
Dear Francois, Francisco, Antreas, hP is the orthoassociate of P i.e. the inverse of P in the polar circle. see my paper about orthocorrespondence. Best
Thanks you Eric The product of X(4) and X(99) is the Miquel point of the orthic axe, tripolaire of X(4); this points belongs the the Steiner Ellips Where is