For explanations, please watch the Youtube video:[br][list][*][url=https://youtu.be/PbA4Js3qKOQ]Orthocenters exist! | Universal Hyperbolic Geometry 10 | NJ Wildberger[/url][/*][/list]

[b]Example [/b]in the triangle [b]a1a2a3 [/b]:[br][list][*]Altitude of [b]a1 [/b]point on the line ([b]a2a3[/b]) [br][/*][/list]