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Johann Rahn[1] (Latinised form Rhonius) (10 March 1622 – 25 May 1676) was a Swiss mathematician who is credited with the first use of the division sign, ÷ (a repurposed obelus variant)[2] and the therefore sign, ∴.[3] 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. It is uncertain whether Rahn or Pell was responsible for introducing the symbols.
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: 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 ScribaJohn 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 StedallA Discourse Concerning Algebra: English Algebra to 1685, Oxford University Press, Oxford, 2002
