Introduction to qualitative and quantitative methods for ordinary and partial differential equations. The following topics are treated with illustrative applications in physics, engineering and biology. Ordinary differential equations: first order, second order with constant coefficients, power series representations, the Frobenius method, the method of variation of parameters. Orthogonal functions and Fourier series. Sturm-Liouville problems. Eigenfunction expansions. Bessel's
equation. Partial differential equations: The method of characteristics. Classification. The method of separation of variables. The heat equation. The wave equation. Laplace's equation. Applications of Bessel functions and Legendre polynomials.