The first use of the term "method of variations" came in 1755 through the work of a young Joseph Louis Lagrange ; Euler presented Lagrange's approach to the Berlin Academy in 1756 as the " calculus of variations ". Unlike Euler, Lagrange's approach was purely analytic rather than geometrical. Lagrange introduced the idea of variation of entire curves or paths between the endpoints than of individual coordinates. For this he introduced a new form of a differential, written δ δ , that acts on integrals rather than d acting on coordinates. His notation continues to be used today.