A proof without words Nov 23, 2020 Via nRICH: A circle touches the lines OA extended, OB extended and AB where OA and OB are perpendicular. Show that the diameter of the circle is equal to the perimeter of the triangle. $\blacksquare$ A selection of other posts Nov 26, 2018 The Mathematical Ninja and the Variable Volume Aug 15, 2018 Ask Uncle Colin: A Trigonometric Proof Dec 1, 2014 Why you can’t get unlimited chocolate (at least like this) Apr 26, 2012 Quotable maths - Goethe subscribe via RSS