Johann Rahn (Latinised form Rhonius) (10 March 1622 – 25 May 1676) was a Swiss

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

who is credited with the first use of the

division sign The division sign () is a symbol consisting of a short horizontal line with a dot above and another dot below, used in Anglophone countries to indicate mathematical division. However, this usage, though widespread in some countries, is not u ...

, ÷ (a repurposed

obelus An obelus (plural: obeluses or obeli) is a term in typography that refers to a historical mark which has resolved to three modern meanings: * Division sign * Dagger * Commercial minus sign (limited geographical area of use) The word "obel ...

variant) and the

therefore sign In logical argument and mathematical proof, the therefore sign, , is generally used before a logical consequence, such as the conclusion of a syllogism. The symbol consists of three dots placed in an upright triangle and is read ''therefore''. Whi ...

, ∴. The symbols were used in ''Teutsche Algebra'', published in 1659. John Pell collaborated with Rahn in this book, which contains an example of the

Pell equation Pell's equation, also called the Pell–Fermat equation, is any Diophantine equation of the form x^2 - ny^2 = 1, where ''n'' is a given positive nonsquare integer, and integer solutions are sought for ''x'' and ''y''. In Cartesian coordinates, ...

. It is uncertain whether Rahn or Pell was responsible for introducing the symbols.

Books

Teutsche Algebra
- Johann H. Rahn

Literature

*R. Acampora ''Johann Heinrich Rahn und seine Teutsche Algebra'', in R. Gebhardt (Herausgeber) ''Visier- und Rechenbücher der frühen Neuzeit'', Schriften des Adam-Ries-Bundes Annaberg-Buchholz 19, 2008, S. 163–178 *

Moritz Cantor Moritz Benedikt Cantor (23 August 1829 – 10 April 1920) was a German historian of mathematics. Biography Cantor was born at Mannheim. He came from a Sephardi Jewish family that had emigrated to the Netherlands from Portugal, another branch o ...

: Rahn, Johann Heinrich . In: General German Biography (ADB). Volume 27, Duncker & Humblot, Leipzig, 1888, pp. 174 f *Noel Malcolm, Jacqueline Stedall ''John Pell (1611–1685) and His Correspondence with Sir Charles Cavendish: The Mental World of an Early Modern Mathematician'', Oxford University Press, Oxford, 2005 *

Christoph Scriba Christoph J. Scriba (6 October 1929 – 26 July 2013) was a German historian of mathematics. Life and work Scriba was born in Darmstadt and studied at ''Justus-Liebig-University Giessen''. He read James Gregory's early writings on the calcu ...

''John Pell's English Edition of J. H. Rahn 's Teutsche Algebra'', in: R. S. Cohen (Herausgeber) ''For Dirk Struik'', Reidel: Dordrecht 1974, S. 261–274 *

Jacqueline Stedall Jacqueline Anne "Jackie" Stedall (4 August 1950 – 27 September 2014) was a British mathematics historian. She wrote nine books, and appeared on radio on BBC Radio 4's ''In Our Time'' programme. Early life Stedall was born in Romford, Essex ...

''A Discourse Concerning Algebra: English Algebra to 1685'', Oxford University Press, Oxford, 2002

References

;general * Cajori, Florian. ''A History of Mathematical Notations''. 2 volumes. Lasalle, Illinois: The Open Court Publishing Co., 1928–1929 vol. 2, page 211. ;citations 1622 births 1676 deaths 17th-century Swiss mathematicians {{Europe-mathematician-stub

Books

Literature

See also

References