L'H?pital's law (L'H? Pitard's Law) is a method to determine the uncertainty under certain conditions by taking the derivative and limit of the numerator and denominator respectively. The French mathematician L'H?pital (Marquis de l'H? Pital) published this rule in his book Analysis of Curves des Infinitesimal Analysis in 1696, so it was named after him. But it is generally believed that this law was first discovered by L'H?pital's teacher and Swiss mathematician johann bernoulli, so it is also called Bernoulli's law.