credited with the first use of the division symbol, ÷ 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