For explanations about the Desargues polar of a point P w.r.t to a triangle, watch the Youtube video:[br][list][*][url=https://youtu.be/PbA4Js3qKOQ]Orthocenters exist! | Universal Hyperbolic Geometry 10 | NJ Wildberger[/url][/*][/list][list][*]pg 10: @34:35 Establishing the polar of a point with respect to a triangle; cevian lines; the Desargue polar[br][/*][/list]