Calculus of variations

The calculus of variations is a field of mathematical analysis. It usually deals with functions defined on the real numbers, and with finding minima and maxima of such functions. When finding a minimum or maximum, there are often additional conditions that need to be satisfied. In the 18th century, mathematicians such as Leonhard Euler and Joseph-Louis Lagrange made this kind of calculus popular. 
Other people who influenced it include Adrien-Marie Legendre, Alfred Clebsch, Carl Gustav Jacob Jacobi and Karl Weierstraß. Today, calculus of variations is used in different fields of science, such as geodesy, theoretical physics, classical mechanics and quantum mechanics.