Sobre a passagem do estudo de função de uma variável real para o caso de duas variáveis

Abstract

This research was developed with the goal of verifying the difficulties and the knowledge shown by students related to the transition of the study of functions of one variable to the case of two variables, regarding dependent and independent variables well as the interdependence between them, to the dominion and the graphic, to the relation between the graphic of the dominion of the function and also which manifestations are revealed in the study of the partial derivatives of the first order. In order to do so we developed two questionnaires based upon the Theory of the Registers of Semiotic Representation of Raymond Duval, the questionnaires having been answered by students of the fourth and fifth term of the course of Mathematics of a private university in the greater São Paulo area. The first questionnaire was applied to students of the fourth term and it made possible to verify not only one first analysis of their difficulties, but also how pertinent the questions were, as well as how fitting the wording was. It has been found that some of the questions needed rephrasing, and also that the addition of new questions was necessary, which contributed to the making of a new questionnaire, which was answered by students of the fifth term. This research revealed some difficulties that students show when studying functions of two variables, such as the comprehension of the system of the 3D axis, the lack of clarity when determining and representing the dominium of the function, difficulty when performing the conversion from the representation of the natural language to the algebric language in contextualised situations, the confusion between the graphic representation of the dominion and the function, and the obstacles for the interpretation of the graphic of a function of two variables, difficulties that have negative effect on the study of partial derivatives. The registers of semiotic representation proved themselves an efficient tool for the explanation of the knowledge and the complexity that the study of functions with two variables represent for students