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Guillaume De l'Hôpital By: Alex Asay. http://www.gap-system.org/~history/Posters2/De_L%27Hopital.html. Background Information. Born in Paris in 1661 Parents were Anne-Alexandre de l'Hospital and Elizabeth Gobelin Became the nobleman of St. Mesme Great at math while growing up
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Guillaume De l'Hôpital By: Alex Asay http://www.gap-system.org/~history/Posters2/De_L%27Hopital.html
Background Information • Born in Paris in 1661 • Parents were Anne-Alexandre de l'Hospital and Elizabeth Gobelin • Became the nobleman of St. Mesme • Great at math while growing up • Stunned math geniuses by the time he was 15 • Solving an “impossible” problem
Other Background Information • Served as a cavalry officer in the French Army • Had to resign because of his near-sightedness • He hired Bernoulli in 1691 to teach him more about math, which he devoted himself
Spark of Fame • l'Hôpital became famous for writing a book Analyse des infiniment petits pour l'intelligence des lignes courbes (Analysis of the Infinitely Small to Learn about Curved Lines) • Sparked controversy after five years • Bernoulli claimed the ideas behind • This book contained “l'Hôpital’s Rule”
The Beginning • The first chapter jumps right into two definitions: • Definition 1: “Variable quantities are those that increase or decrease continuously while a constant quantity remains the same while other vary.” • Definition 2: “The infinitely small part by which a variable quantity increases or decreases continuously is called the differential of that quantity.”
The Beginning • After this, it moves onto two axioms (commonly accepted principles and rules): • Axiom 1: “Grant that two quantities whose difference is an infinitely small quantity may be taken (or used) indifferently for each other; or (what is the same thing) that a quantity which is increased or decreased only by an infinitesimally small quantity may be considered as remaining the same.” • Axiom 2: “Grant that a curved line may be considered as the assemblage of an infinite number of infinitely small straight lines; or (what is the same thing) as a polygon with an infinite number of sides, each of infinitely small length such that the angle between adjacent lines determines the curvature of the curve.”
“l'Hôpital’s Rule” • It states a method for finding the limit of a rational function that has both a denominator and numerator of zero at a point. • If the limit of f(x) as x approaches c which equals the limit of g(x) as x approaches c which equals 0 or the limit of g(x) equals plus or minus infinity and the limit of f’(x) divided by g’(x) as x approaches c exists, then the limit of f(x)/g(x) as x approaches c equals the limit of f’(x)/g’(x) as x approaches c.
Requirements of the Limit • In order for “l'Hôpital’s Rule” to exist, the limit of f’(x)/g’(x) as x approaches c must exist
The Rule in Numerical Form http://www.camotruck.net/rollins/math/lhopital-h.gif
Results of the Controversy • l'Hôpital was wrong! • In 1921, an early Bernoulli manuscript was discovered revealing very similar traits to the items discussed in l'Hôpital’s book • On March 17, 1694, he sent a letter to Bernoulli asking him if he would stay quiet about the dilemma if he would get paid. • Basically, l'Hôpital bribed Bernoulli to shut up!!! • Bernoulli accepted
Additional Fame • Found the solution to the brachystochrone (the curve of the fastest decent in a gravitational field of a weighted particle that is moving between two points) • The problem was solved by others including Newton, Leibnitz, and Jacob Bernoulli
Additional Fame • He also published a rule on analytical conics in 1707 that was considered to be the standard reference for that topic for about 100 years.
The l'Hôpital Legacy • l'Hôpital died in Paris on February 2, 1704. • It is believed that he was a generous, modest, and charismatic man • He had three kids with his wife Marie-Charlotte de Romilley de La Chesnelaye.
Cited Sources • World of Mathematics. World of Mathematics on Guillaume Francois Antoine L'Hospital. Guillaume Francois Antoine L'HospitalBiography. http://www.bookrags.com/biography/guillaume-francois-antoine-lhospital-wom/ • l'Hôpital's rule. May 15, 2009. <http://en.wikipedia.org/wiki/L'H%C3%B4pital's_rule> • Kensington Intermediate Senior High. <http://www.edu.pe.ca/kish/Grassroots/math/guillaum.htm>
Additional Cited Sources • JOC/EFR. 2008. < http://www-history.mcs.standrews.ac.uk/Biographies/De_L'Hopital.html> • Dictionary.com, LLC. <http://dictionary.reference.com/browse/axioms>