Elements of the Visualisation Process within a Dynamic Geometry Environment

The advent of powerful computer graphic packages has coincided with renewed interest in all forms of visual representation in mathematics. As a result, we need to be clear about what we mean by the visual processing necessary to solve mathematical problems involving visual phenomena. Visual processing involves the ability to mentally manipulate and transform visual representations and visual imagery. This paper describes three different elements of the visualisation process: crude visualisation, visualisation as the reading of visual information, and visual processing. Illustrations are given of how the use of a dynamic geometry package such as Cabri-Géomètre both needs and contributes to developing visualisation in all these three senses.