This book is devoted to the analysis of approximate solution techniques
for differential equations, based on classical orthogonal polynomials.
These techniques are popularly known as spectral methods. In the last
few decades, there has been a growing interest in this subject. As a
matter offact, spectral methods provide a competitive alternative to
other standard approximation techniques, for a large variety of
problems. Initial ap- plications were concerned with the investigation
of periodic solutions of boundary value problems using trigonometric
polynomials. Subsequently, the analysis was extended to algebraic
polynomials. Expansions in orthogonal basis functions were preferred,
due to their high accuracy and flexibility in computations. The aim of
this book is to present a preliminary mathematical background for be-
ginners who wish to study and perform numerical experiments, or who wish
to improve their skill in order to tackle more specific applications. In
addition, it furnishes a com- prehensive collection of basic formulas
and theorems that are useful for implementations at any level of
complexity. We tried to maintain an elementary exposition so that no
experience in functional analysis is required.