Let ABC be a triangle, A'B'C', A"B"C" the antipedal tiangles of H, O [antimedial, tangential, resp.].
3. ABC, Triangle A*B*C* bounded by the lines (A'A",B'B",C'C") are perspective.
[the perspector is on the circumcircle(ABC) = NPC(A'B'C') = Incircle(A"B"C")]
Antreas P. Hatzipolakis, Hyacinthos #21780