Whose theorem states that if an odd prime number is divisible by four and leaves a remainder of one, it is always the sum of two square numbers?
Pierre de Fermat
Oh no! Not math! Anything but math! Born at the turn of the 17th century, French lawyer and mathematician Pierre de Fermat discovered not only this theorem but also fundamental principles for geometry, calculus and probability that we still use to this day. Well, maybe you don’t use them every day, but that doesn’t mean they aren’t used. Rocket scientists, quantum physicists and insurance actuaries probably love Pierre de Fermat, right? Source: Encyclopedia Britannica
Pierre de Fermat (French: [pjɛːʁ də fɛʁma]; (Between 31 October and 6 December 1607 – 12 January 1665) was a French lawyer at the Parlement of Toulouse, France, and a mathematician who is given credit for early developments that led to infinitesimal calculus, including his technique of adequality.