Jean Paul de Gua de Malves

Jean Paul de Gua de Malves, known as Gua, was a French mathematician, born in 1713 at Malves-en-Minervois in Aude and dead on 2 June 1785. He was the son of Jean de Gua, baron de Malves, and Jeanne de Harrugue; his father was ruined by the speculations of John Law Company and had to sell his estates. Gua became a priest and mathematician. In 1740 he published a work on analytical geometry in which he applied geometry, without the aid of differential calculus, to find the tangents, asymptotes and various singular points of an algebraic curve. He further showed how singular points and isolated loops are affected by conical projection. He gave the proof of Descartes rule of signs found in most modern works; it is not clear whether Descartes ever proved it strictly, and Newton seems to have regarded it as obvious. Gua was acquainted with many of the French philosophes during the last decades of the Ancien Régime.