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Johann Rahn (Latinised form Rhonius) (1622–1676) was a (* 10 March 1622 Töss (Winterthur), † 25 May 1676 in Zurich) Swiss mathematician who is credited with the first use of the division symbol, ÷ (obelus) and the therefore sign, ∴. He is known for his Teutsche algebra, the first time the Geteiltzeichen characters appear in print. The symbol is used in Teutsche Algebra, published in 1659. John Pell collaborated with Rahn in this book, which contains an example of the Pell equation, Pell-loading of the English translation of the book of Rahn. There is a controversy in Pell awards, rather than Rahn, authorship notations. Rahn was also, it seems, mayor of the city of Zurich in 1655.
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