Desargues, Gérard

(1593-1662)

   engineer, mathematician

   Born in lyon, Gérard (or Gespard) Desargues was dedicated to research in pure geometry and was the first to understand the fundamental role of perspective. He gave, after Apollonios, the basis for the projective geometry of conic sections (Brouillon project d'une atteinte aux événements des rencontres du cône avec un plan, 1639). Among his most important conclusions, he was able to prove the idea that all conic forms can be considered as the projection of a circle, the concept of an infinite point in a right angle, the subsequent identification of a cluster of parallel right angles, and a cluster of concurrent right angles, as well as that of a cone and a cylinder, the theory of the involution on a right angle and the Desargues Theorem on homologic triangles.