Johann Heinrich Rahn

Johann Heinrich Rahn, also known as Hans Heinrich Rahn and Johann Rahn, lived from 1622 to 1676 and was a Swiss mathematician who is credited with the first use of the division sign, a repurposed obelus variant, and the therefore sign. The symbols appeared in the Teutsche Algebra of 1659, a book on which John Pell collaborated with him, and it is uncertain whether Rahn or Pell introduced them. Born in Töss in the canton of Zurich into a prominent burgher family, he entered the city's Grand Council in 1642 and its Small Council in 1669 and held several public offices, including Landvogt of Kyburg and head of the arsenal. John Pell, Cromwell's diplomatic representative in Zurich, introduced him to algebra between 1654 and 1658, and the Teutsche Algebra became the first German-language presentation of the algebra of Viète and Descartes. Thomas Brancker published an English translation in 1668. Rahn was also interested in astronomy and optics and studied the prediction of eclipses and the passage of comets.