Sandifer has been studying Euler for decades and is one of the world s leading experts on his work. This volume is the second collection of Sandifer's How Euler Did It columns. Each is a jewel of historical and mathematical exposition. The sum total of years of work and study of the most prolific mathematician of history, this volume will leave you marveling at Euler's clever inventiveness and Sandifer's wonderful ability to explicate and put it all in context.