ABSTRACT
Regular perturbation methods are very useful for evaluating the effect of various kinds of perturbations. However, the application of these methods is strongly limited by our capacity to construct and analyze solutions of the unperturbed problem, the so-called generating problem, and require numerical analysis (see Sections 1.3, 2.3, 2.10). One of the simplest classes of perturbed problems is that of systems with slowly varying parameters which are close to constants. For such problems it is possible to obtain fairly complete theoretical results and relatively concise formulas, often with explicit analytical expressions.
