STEP 1 - WRAP RIBBON: Take the ribbon and wrap it around a glass. Mark where the ribbon overlaps itself. Image caption, STEP 2 - CUT CIRCUMFERENCE: Cut the ribbon at the point where it overlaps. You ...

MATHEWS, G. A Triangle that gives the Area and Circumference of any Circle, and the Diameter of a Circle equal in Area to any given Square. Nature 93, 110 (1914 ...