Calculus Without Hocus Pocus

Book excerpt: Calculus is a subject that needs to be studied many times over, ideally with a different book in each new round. Using Ezra Pound’s analogy (in ABC of Reading), we may think of the learner as an apprentice carpenter, and of calculus as a stool or table; the learner must keep going until the piece of furniture has three legs and will stand up, or four legs and won’t tip over too easily. Most people cannot follow this plan, because life is short and the list of other demands on their time just too long. This book has been written with a view to making calculus more interesting and intelligible to those who left college, recently or a long time ago, without becoming an adept; those who are familiar with the contents of undergraduate calculus, but not altogether content with their own grasp of the central concepts; those who are aware that the structure put together by them during their apprenticeship is too wobbly, and liable to tip over when the number of independent variables is increased from one to just two. An absurd simile? Not in the opinion of a distinguished mathematician and educator (quoted verbatim in the preface), who acknowledged that the customary definition of a differential in the theory of functions of a single variable breaks down when one extends it to functions of several variables and considers double integrals. He continued: “Students are rightly baffled when they attempt to convert such an integral to polar coordinates and are told that no longer is it permissible to [apply a straightforward extension of the relevant formula for a change of variable in a single integral]. The Jacobian must be used instead, and at this point the logical structure which was built so carefully collapses entirely. If we wish to make calculus an intellectually honest subject and not a collection of convenient tricks, it is time we made a fresh start.” Calculus Without Hocus Pocus aims to elucidate those (and only those) issues that are not treated adequately in standard textbooks. It offers more cogent explanations of the conundrums and paradoxes which have been nagging the minds of students and teachers of calculus for generations. The author, who has been using calculus as a teacher and researcher for over fifty years, has tried to produce a condensed and readable book that throws light from various directions upon the difficult parts of this very technical (and somewhat unpopular) subject; to show some of the reasons why calculus has been cast in the mould in which we find it; and to recommend some minor changes in notation and nomenclature that would remove nearly all of the hocus-pocus which almost every learner of calculus has had to endure so far.