""Introduction to the Calculus of Variations"" is a book written by William Elwood Byerly and first published in 1917. The book is a comprehensive introduction to the study of calculus of variations, which is a branch of mathematics that deals with finding the optimal solution to a given problem. The book covers a range of topics including the basic principles of the calculus of variations, the Euler-Lagrange equation, the Hamiltonian formulation,...