A discrete approach to the concept of derivative

Abstract

The concept of derivative is a basic concept of calculus. It is closely related to the concept of function, the idea of rate of change, and the limit concept. In recent decades, teaching the concept of derivative in mathematics classrooms has changed: a quite formal approach—closely linked to the teaching of calculus at university and based on the sequence concept—has been transformed to or substituted by a new one. This means working with rates of change, an intuitive access to the concepts of limit and derivative. It includes working with real functions right from the beginning, a great emphasis on graphs, and the use of digital technologies. The meaning of sequences has decreased to a point where they are sometimes no longer even taught in the calculus course. In recent years this concept has been criticized for not developing adequate perceptions of the basic concepts of calculus and not sufficiently preparing the students for scientific courses at university. In this paper we present an alternative discrete step-by-step approach to the basic concepts of calculus by working with sequences and difference sequences, functions defined on $\mathbb{Z}$ and discrete domains of $\mathbb{Q}$, and by subsequently developing the concept of rate of change in a discrete learning environment. The paper is based on general theoretical considerations and empirical investigations by the author and is meant as a contribution to classroom design-research or “design science” (Wittmann, Educ Stud Math 29(4):355–374, 1995).