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 30, 2018 Ask Uncle Colin: Sketching in 3D Apr 18, 2018 Ask Uncle Colin: Tangents to a circle Dec 15, 2014 A “Proof” that 1 = 2 May 31, 2012 Quotable maths - Whitehead subscribe via RSS