World Bank economist Kaushik Basu has proved that when it comes to right triangles, a² + b² = c². This merits the briefest of footnotes in the annals of mathematics, because the Greek mathematician Pythagoras proved the same theorem around 500 B.C. Every kid in geometry class learns that the sum of the squares of the lengths of the sides of a right triangle equals the square of the length of the hypotenuse. This is noFermat's Last Theorem.
It's kind of impressive nonetheless. Basu now belongs to an august tradition of people who have found new ways of proving something we have known for 2,600 years. Amazingly, a U.S. president was one of the provers. James Garfield completed his proof of the Pythagorean theorem in 1876, four years before being elected president. (ThisKhan Academy video gives the presidential derivation.)
