""Researches In The Calculus Of Variations, Principally On The Theory Of Discontinuous Solutions: An Essay"" is a book written by Isaac Todhunter and published in 1871. The book is a thorough exploration of the calculus of variations, which is a branch of mathematics concerned with finding the extrema of functionals. The focus of the book is on the theory of discontinuous solutions, which involves finding solutions to problems where the function being...