Rhonius

Johann Rahn (Latinised form Rhonius) (10 March 1622 – 25 May 1676) was a Swiss mathematician who is credited with the first use of the division symbol, ÷ (obelus) and the therefore sign, ∴. 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. Rahn was also, it seems, mayor of the city of Zurich in 1655.

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