l'Analyse des Infiniment Petits pour l'Intelligence des
Lignes Courbes (literal translation: Analysis of the
infinitely small to understand curves) (1696), is the first European book about differential calculus. It was
written by the French mathematician Guillaume de l'Hôpital
In this book is the first appearance of L'Hopital's rule.
The rule is believed to be the work of Johann Bernoulli since l'Hôpital, a nobleman, paid Bernoulli a retainer of 300₣ per year to keep him updated on developments in calculus and to solve problems he had. (Moreover, the two signed a contract allowing l'Hôpital to use Bernoulli's discoveries in any way he wished.)^{[1]} ^{[2]} Among these problems was that of limits of indeterminate forms. When l'Hôpital published his book, he gave due credit to Bernoulli and, not wishing to take credit for any of the mathematics in the book, he published the work anonymously. Bernoulli, who was known for being extremely jealous, claimed to be the author of the entire work, and until recently, it was believed to be so. Nevertheless, the rule was named for l'Hôpital, who never claimed to have invented it in the first place^{[3]}.
