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 Jul 23, 2018 Can you find a centre and angle of rotation without any construction? Dec 24, 2015 Wrong, But Useful: Episode 31 Nov 12, 2014 Radians (and why they are better than degrees) Aug 1, 2013 Wrong, But Useful: Episode 5 subscribe via RSS