Guillaume de l'Hôpital

Guillaume François Antoine, Marquis de l'Hôpital, was a French mathematician, born on 7 June 1661 and dying on 2 February 1704, whose name is firmly attached to l'Hôpital's rule for limits of the indeterminate forms 0 over 0 and infinity over infinity. The rule did not originate with him, but it appeared in print for the first time in his 1696 treatise on the infinitesimal calculus, Analyse des Infiniment Petits pour l'Intelligence des Lignes Courbes, the first systematic exposition of differential calculus and a model for later treatments. He came from a military family and left the army because of poor eyesight. In 1691 he met Johann Bernoulli in Nicolas Malebranche's circle in Paris, and Bernoulli supplemented his Paris talks with private lectures at l'Hôpital's estate. Elected to the French Academy of Sciences in 1693, he corresponded with Leibniz, Huygens and Jacob Bernoulli. His treatise on conic sections appeared posthumously in 1707.