11.1 Introduction and Historical Remarks11.2 Eigenvalues and the Vibrating String11.2.1 Boundary Value Problems11.2.2 Derivation of the Wave Equation11.2.3 Solution of the Wave Equation11.3 The Heat Equation11.4 The Dirichlet Problem for a Disc11.4.1 The Poisson Integral11.5 Sturm—Liouville Problems