Rahn was born in
Töss, in the
canton of Zurich, on 10 March 1622, the son of Ursula
Escher vom Glas and Hans Heinrich Rahn,
Amtmann of Töss and future mayor of
Zurich. As the member of a prominent
burgher family of Zurich, he entered the city's Grand Council in 1642 and its Small Council in 1669. Rahn served in a number of public offices in the
canton of Zurich: he was
Landvogt of
Kyburg from 1658 and 1664,
Obervogt of
Küsnacht in 1670, head of the arsenal in 1672 and treasurer in 1674. Rahn's interest in mathematics was likely instilled by .
Oliver Cromwell's diplomatic representative in Zurich,
John Pell, introduced him to the study of algebra between 1654 and 1658. In 1659, Rahn published his
Teutsche Algebra, the first German-language presentation of the new algebraic theories of
François Viète and
René Descartes. The work first discusses the six basic arithmetic operations (
addition,
subtraction,
multiplication,
division,
exponentiation, and
root extraction) and the
theory of equations. Drawing on treatises of earlier mathematicians, it then presents a mixture of equation exercises, in addition to
trigonometric and relatively simple
analytic geometry problems.
Thomas Brancker, with Pell's assistance, published an English translation of
Teutsche Algebra in 1668, which brought the work to widespread circulation. Rahn was also interested in astronomy and optics. He created a draft of a
perpetual calendar and studied the prediction of eclipses and the passage of comets, while opposing
astrology. Rahn died in Zurich on 27 May 1676, aged 54. ==See also==