Based on modern Sobolev methods, this text not only includes an informal introduction that develops students' physical and mathematical intuition, but also introduces Hilbert space in its natural environment, and then poses and solve standard problems. The final part covers Sturm-Liouville problems, Fourier integrals, Galerkin's method, and Sobolev methods. 1994 edition. 64 figures. Exercises.
Here's a sample of other books in this Dover category
Chebyshev and Fourier Spectral Methods: Second Revised Edition by John P. Boyd Completely revised text applies spectral methods to boundary value, eigenvalue, and time-dependent problems, but also covers cardinal functions, matrix-solving methods, coordinate transformations, much more. Includes 7 appendices and over 160 text figures.
Fourier Series by Georgi P. Tolstov This reputable translation covers trigonometric Fourier series, orthogonal systems, double Fourier series, Bessel functions, the Eigenfunction method and its applications to mathematical physics, operations on Fourier series, more. Over 100 problems. 1962 edition.
