This classic text features a sophisticated treatment of Fourier's pioneering method for expressing periodic functions as an infinite series of trigonometrical functions. Geared toward mathematicians already familiar with the elements of Lebesgue's theory of integration, the text serves as an introduction to Zygmund's standard treatise.Beginning with a brief introduction to some generalities of trigonometrical series, the book explores the Fourier series in Hilbert space as well as their convergence and summability. The authors provide an in-depth look at the applications of previously outlined theorems and conclude with an examination of general trigonometrical series. Ideally suited for both individual and classroom study, this incisive text offers advanced undergraduate and graduate students in mathematics, physics, and engineering a valuable tool in understanding the essentials of the Fourier series.