Jean-Robert Argand

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Jean-Robert Argand (born July 18, 1768 in Geneva , † August 13, 1822 in Paris ) was a bookseller and amateur mathematician .

He is the son of jeweler Jacques Argand (an admirer of Jean-Jacques Rousseau ) and Eve Carnac. From 1791 to 1794 he took part in the revolution in the Geneva Republic in various leading positions, for example he was secretary of the Commission of Forty in 1792, from December 1792 member of the provisional administrative committee of the city and from May 1793 its president and in 1794 was judge at the Revolutionary Tribunal and Member of Parliament. He then moved first to Sèvres and later to Paris.

In 1806, Argand published a geometrical interpretation of complex numbers ( Argand diagram ), in which i is seen as a rotation of 90 degrees. This geometric description of the complex numbers is usually named after Carl Friedrich Gauß ( Gaussian plane of numbers ). Before Gauss, however, Caspar Wessel described it as early as 1797 (published in 1799, but also long forgotten). Argand published his account in a privately printed pamphlet (forgetting to put his name on the title page), which Adrien-Marie Legendre became aware of. Legendre mentioned this to the mathematician François Français (without mentioning the name Argand) in a letter. After the death of Français, his papers went to his brother Jacques Français , who found the letter and published the results in the Annales de mathématiques in 1813 . In it he gave Legendre's letter as the source and appealed to the unknown author of the representation to make his name public. This then happened in the next issue by Argand.

In 1814 he gave a simple proof of the Fundamental Theorem of Algebra (Annales des Mathématiques, Volume 5, p. 197), based on the incomplete proof by Jean d'Alembert from the 18th century.

In 1795 he married Françoise-Dorothée Blanc from Lausanne .

Works

  • Essai sur une manière de représenter les quantités imaginaires dans les constructions géométriques . Paris 1806 (2nd edition 1874).

Web links

Individual evidence

  1. ↑ Orlando Merino , A short history of complex numbers, University of Florida 2006 (pdf)
  2. ↑ For example in Reinhold Remmert , Fundamentalsatz der Algebra, in: D. Ebbinghaus u. a. (Ed.), Numbers, Springer, 1983, p. 89ff, and also in Mangoldt, Knopp, Introduction to Higher Mathematics, Volume 2, 1958.
personal data
SURNAME Argand, Jean-Robert
BRIEF DESCRIPTION mathematician
DATE OF BIRTH July 18, 1768
PLACE OF BIRTH Geneva
DATE OF DEATH August 13, 1822
Place of death Paris