 The advent of infinitesimal calculus led to a general formula that provides closed-form solutions in some cases.A curve in the plane can be approximated by connecting a finite number of points on the curve using line segments to create a polygonal path.Since it is straightforward to calculate the length of each linear segment (using the Pythagorean theorem in Euclidean space, for example), the total length of the approximation can be found by summing the lengths of each linear segment; that approximation is known as the "(cumulative) chordal distance".