Hidden harmonies

A squared plus b squared equals c squared. It sounds simple, doesn't it? Yet this familiar expression is a gateway into the riotous garden of mathematics, and sends us on a journey of exploration in the company of two inspired guides, who trace the life of the Pythagorean theorem from ancient Babylon to the present, visiting along the way Leonardo da Vinci, Albert Einstein, President James Garfield, and the Freemasons--not to mention the elusive Pythagoras himself. Why does this theorem have more than two hundred proofs--or is it four thousand? And it has even more applications than proofs:…