Pierre Varignon , born with Caen in 1654 and died in Paris the December 23rd 1722, is a Mathématicien French.

Biography

Wire of a Architect, Pierre Varignon was one of the geometrician S French most famous of his time. Intending itself for the priesthood, he studies the Théologie and the Philosophie with the college Jesuit of Caen when the reading of a Euclide which fell to him under the hand woke up its taste for mathematics. The reading of the works of Descartes completed to determine its choice. Ordered priest, it came to Paris in 1686 with the abbot from Saint-Pierre who made him a pension of 300 pounds. Its Projet of a new mechanics is worth to him a pulpit of Mathématiques to the college Mazarin. In November 1688, he becomes member of the section of geometry of the royal Académie of sciences. It is named first holder by Louis XIV, the January 28th 1699. In 1706, it succeeds Jean-Baptiste Of Hamel in his pulpit of Greek and Latin philosophy to the Collège de France. Of 1710 with 1712, he is sub-manager, then directing until in 1719 of this Academy. He is elected with the Académie of Berlin in 1713 and with the Royal Society in 1718. The correspondence which it maintained with Leibniz, Newton and especially the brothers Bernoulli enabled him to become, in.liaison.with the marquis of the Hospital, one of the most active promoters of the introduction in France of differential and integral calculus created by Leibniz.

Work in mathematics

It created the theorem which bears its name by showing that the figure obtained by uniting the mediums on the sides of a unspecified Quadrilatère is a Parallélogramme. By uniting the mediums on the sides of a square, one obtains a second square. While making in the same way with a rectangle, one obtains a rhombus (in the same way with a rhombus, one obtains a rectangle).

These properties are in fact only obvious consequences of the Théorème from Thalès and were certainly known before Varignon.

Work in physical sciences

Mechanical statics

In 1688, it showed the rule of composition of the convergent forces stated by Simon Stevin.

Kinematic

It formalized the definitions of the instantaneous Speed and the Accélération.

In two communications with the royal Academy of sciences, the July 5th 1698 then the January 20th 1700 it first of all defines the concept instantaneous speed (which it names speed in each moment) then that of acceleration by applying the differential Calculus of Leibniz to the trajectory of a body. It finally shows, using this same differential calculus, that it is possible to deduce acceleration from a body starting from its instantaneous speed by a simple operation of derivation.

Surprisingly, these results were so quickly adopted by the scientific community of its time that their author was forgotten a little. However, by exceeding the geometrical methods of resolution of the problems of mechanics of the solid, it opened the way with D' Alembert and Lagrange to still write the statements of physics of use today. For this reason, Varignon can thus be regarded as one of the founders of the analytical mechanics.

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