Johann Rahn
Johann Heinrich Rahn, Hans Heinrich Rahn, Latinized Rhonius, ( born March 10, 1622 Töss (today Winterthur), † May 25 1676 in Zurich ) was a Swiss mathematician. He is known for his Teutsche algebra, in the first time the Divided character appears in printed form.
Life
He was the son of Hans Heinrich Rahn (1593-1669), then bailiff in Töss, later (1655-1669) Mayor of Zurich, and the Ursula Escher from the glass ( 1591-1663 ). His uncle Hans Rudolf Rahn (1595-1655) was also mayor of Zurich ( 1644-1655 ). Rahn was 1642 representatives of Aries guild in the Great Council of the City of Zurich and was from 1669 also in exclusive small council of Zurich. 1651, he was Unterzeug Lord and used Swedish artillery ( Bern fields artillery ) were under his direction bought at this time. In 1658 he was bailiff of the bailiwick of Kyburg, which he remained until 1664, when he opened a silk factory in Zurich at Neumarkt. In 1670 he was Obervogt of Küsnacht, 1672 top toys 1674 Mr. and treasurer.
He married in 1642, the pastor's daughter Elisabeth Holzhalb ( born 1626 ) and had with her two sons, Hans Heinrich ( born 1646) and Hans Rudolf ( born 1669).
Rahn's interest in mathematics was stimulated probably by his uncle Hans Georg Werdmüller (1616-1678), a military engineer, the construction of the fortifications of Zurich conducted from 1642 to 1675. He was from 1654 by John Pell introduced into the algebra, which was from 1654 to 1658 representatives of Oliver Cromwell in the Protestant cantons of Switzerland, with the mission of these secede from the alliance with the Catholic cantons. With Pell he had an exchange of letters, which is partially preserved ( with a first letter of November 1654). Regular classes of Pell he received probably from 1657 - according to John Aubrey's biography of Pell came Rahn every Friday night for instruction in Zurich - and ended in early 1658, when Rahn bailiff was in Kyburg.
1659 Rahn published his Teutsche algebra, in which the algebraic methods of François Viète and René Descartes were first shown in German language. Other problems he took the works of Frans van Schooten, Diophantus and Christopher Clavius . The book was also under the influence of the teaching of Rahn's teacher John Pell - a thanksgiving to Pell (without mention of the name, because it did not want it ) can be found in the preface. In the book there is also the first time in printed form the Divided sign ( ÷ ). It covers the resolution of equations in addition to elementary arithmetic and analytic geometry. Also a form of Pell equation can be found in it.
Further dissemination found the book published in 1668 by the English translation by Thomas Brancker, assisted by John Pell ( the significant parts about newly contributed to the extent of half of the book, but did not want to be named as co-author ). Pell encouraged the translation of, after he had received the book in 1660 - he saw it as a modern algebra text when the then standard English work of William Oughtred ( Clavis Mathematicae, 1631). By translating the Shared characters became widespread in the English -speaking world. The translator Brancker originally had it replaced by another symbol, but at the insistence of Pell he sat back on the original character.
There is also an extended Latin version of the algebra of 1667 ( Algebra Speciosa seu Introductio in Geometriam universal ), but which he did not publish after the appearance of the English translation, but deposited in the municipal library of Zurich.
He also studied astronomy ( prediction of eclipses and comets ) and designed a perpetual calendar. He was an opponent of astrology. Rahn also wrote a book ( in Latin) on the problems of Diophantus ( intended as a supplement to the Latin edition of his Algebra ) and a book on optics; but both are not received.