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 May 5, 2021 Ask Uncle Colin: Couples Jul 15, 2019 A folding puzzle Aug 23, 2017 Ask Uncle Colin: An Uncommon Logarithm Jun 26, 2013 Book review: Mathematics: A Novel subscribe via RSS