For explanation, you can watch the following YouTube videos :[br][list][*][url=https://youtu.be/AjVM5Q-pvjw]Apollonius and polarity | Universal Hyperbolic Geometry 1 | NJ Wildberger[/url][/*][*][url=https://youtu.be/N2T0bg_DJLQ]Duality and perpendicularity | Universal Hyperbolic Geometry 9 | NJ Wildberger[/url][/*][/list]