Clavis mathematicae

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{{Short description|Mathematics book written by William Oughtred}}

Clavis mathematicae (English: The Key of Mathematics) is a mathematics book written by William Oughtred, originally published in 1631 in Latin. It was an attempt to communicate the contemporary mathematical practices, and the European history of mathematics, into a concise and digestible form. The book contains an addition in its 1647 English edition, "Easy Way of Delineating Sun-Dials by Geometry", which had been written by Oughtred earlier in life. The original edition brought the autodidactic Oughtred acclaim amongst mathematicians, but the English-language reissue brought him celebrity, especially amongst tradesman who made use of the arithmetic in their labors. The book is also notable for using the symbol "x" for multiplication, a method invented by Oughtred.{{Cite web|title=Mathematical Treasure: William Oughtred's The Key of the Mathematicks {{!}} Mathematical Association of America|url=https://www.maa.org/press/periodicals/convergence/mathematical-treasure-william-oughtred-s-the-key-of-the-mathematicks|access-date=2022-02-20|website=www.maa.org}}{{Cite web|title=Clavis Mathematicae {{!}} work by Oughtred {{!}} Britannica|url=https://www.britannica.com/topic/Clavis-Mathematicae|access-date=2022-02-20|website=www.britannica.com|language=en}}