# How To Prove A Geometric Formula With A Clementine And A Piece of Paper

Here's a fun demonstration from Cornell maths professor Steven Strogatz. Take a clementine (or any spherical, peelable fruit) and trace around its widest part four times. Then peel it. Flatten out the peelings as best you can and divvy them up evenly among the circles. Voilà! Tangible proof that the the surface area…