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 Mar 22, 2021 A Continued Fraction for $e$ Aug 14, 2017 An Integral Diversion Oct 6, 2014 An awkward inequality Apr 5, 2013 Carnival of Mathematics 97 subscribe via RSS