Théorème de GULDIN_Démonstration

Guldin's First Theorem: The surface area generated by a plane curve C rotating around an axis  of its plane P, not crossing it, is equal to the product of the curve's length times the perimeter of the circle described by its center of gravity. Guldin's Second Theorem: The volume generated by a plane surface S rotating around an axis  of its plane, not crossing it, is equal to the product of the surface area times the perimeter of the circle described by its center of gravity.