Historically, this result first appeared in l'Hospital's 1696 treatise, which was the first textbook on differential calculus .
Within the book, l'Hospital thanks the Bernoulli brothers for their assistance and
their discoveries. An earlier letter by John Bernoulli gives both the rule and its
proof, so it seems likely that Bernoulli discovered the rule (Larson et al. 1999,
L'Hôpital's rule states that for functions f and g which are differentiable on an open interval I except possibly at a point c contained in I , if