Johann Rahn (Latinised form Rhonius) (1622–1676) was a Swiss mathematician who is credited with the first use of the division symbol, ÷ (obelus) and the therefore sign, ∴. The symbol is used in Teutsche Algebra, published in 1659.
* Cajori, Florian. A History of Mathematical Notations. 2 volumes. Lasalle, Illinois: The Open Court Publishing Co., 1928-1929 vol. 2, page 211.
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