Guillaume-Francois-Antoine de L'Hopital
Guillaume-François-Antoine de L’Hopital (1661-1704) was a famous mathematician that has been given credit for coming up with "L’Hopital’s rule". This rule is a method for finding the limit of a rational function whose numerator and denominator tend to zero at a point. L’Hopital was the son of a lieutenant-general in one of the king’s armies. This meant that he was expected to have a military career. He showed no talent in the military and showed extraordinary talent in mathematics. So soon after he was forced to resign from the military due to near-sightedness he devoted all his time to mathematics.
In 1691 he met Jean Bernoulli, one of the few men that understood the new methods of differential calculus in the time period. He taught Guillaume de L’Hopital calculus all through that year. L’Hopital proved to be a very talented mathematician when he solved the brachystochrone problem. This problem had been solved only by people like Newton, Leibnitz, and Jacob Bernoulli.
In 1692 L’Hopital became famous when he wrote the book Analyse Des infiniment petits pour l’intelligence Des lignes courbes. This book was the first book written on differential calculus and included the L’Hopital rule. Even though Guillaume de L’Hopital claimed all the things written in his book were based on his own ideas, his teacher Bernoulli said after L’Hopital’s death the famous rule in the book was his idea. And after the investigation of historical records Bernoulli’s claim was justified. L’Hopital had great wealth and most likely paid for Bernoullis’s silence during the time he lived.