François Walther de Sluze

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René François Walther de Sluze (Slusius), canon of Liège and abbot of Amay, (July 7, 1622 - March 19, 1685) was a Walloon mathematician.

[edit] Biography

He studied at the University of Leuven (1638-1642) and received a master degree in law from the University of Rome, La Sapienza in 1643. There he also studied several languages, mathematics and astronomy. Aside from mathematics he also produced works on astronomy, physics, natural history, general history and theological subjects related to his work in the Church. He became a canon of the Catholic church in 1650, soon after which he became canon of Liège. In 1666 he took a new position as abbot of Amay. While in those positions, he maintained correspondence with Blaise Pascal, Christiaan Huygens, John Wallis, and Michelangelo Ricci. He was elected to the Royal Society in 1674.

[edit] Mathematical contributions

He found for the subtangent of a curve

f(x, y) = 0

an expression equivalent to

${-y {\partial f \over \partial x} \over {\partial f \over \partial x}}$ .

He also wrote numerous tracts, and in particular discussed at some length spirals and points of inflexion. The Conchoid of de Sluze is named after him. He is described by John Wallis in his Algebra as "a very accurate and ingenious person." Several of his works were included in Transactions, e.g. his method of drawing tangents to geometrical curves.