The Birthday of James A. Garfield (1831) – A Pythagorean Theorem Proof

President Garfield (20th US president) was a mathematician. He published a proof of the Pythagorean theorem in 1876 (five years before his assassination). His proof uses a trapezoid with sides a and b, height a+b, and area (a+b)²/2 = area of three right triangles: ab/2 + ab/2 + c²/2 → (a+b)² = 2ab + c² → a² + b² = c². He was proud of it. Garfield was also a teacher and Civil War general. His assassination cut short a presidency that valued mathematics.