Watch the following YouTube videos from Norman J. Wildberger:[br][list][*][url=https://youtu.be/lxVKbntvVlg]Green geometry (I) | WildTrig: Intro to Rational Trigonometry | N J Wildberger[/url][/*][*][url=https://youtu.be/Daz6p5MVG4g]Green geometry (II) | WildTrig: Intro to Rational Trigonometry | N J Wildberger[/url][br][/*][/list]Move the points [b]A1[/b], [b]A2[/b] or [b]A3[/b] of the triangle.