What is the Calculus of Variations?

Many problems involve finding a function that maximizes or minimizes an integral expression.

One example is finding the curve giving the shortest distance between two points -- a straight line, of course, in Cartesian geometry (but can you prove it?) but less obvious if the two points lie on a curved surface (the problem of finding geodesics.)

The mathematical techniques developed to solve this type of problem are collectively known as the calculus of variations.