An inner product space is the natural generalization of the Euclidean space \( \mathbb {R}^{n},\) with its well-known topological and geometric properties. It constitutes the framework, or setting, for much of our work in this book, as it provides the appropriate mathematical structure that we need. Of particular relevance to this study is the subject of sequences of functions and their integrals, hence a quick review of the convergence properties of such sequences is also included.