To produce conjectures and to prove them within a dynamic geometry environment: a case study

This paper analyses a case study of a pair of students working together, who were asked to produce conjectures and to validate them within the dynamic geometry environment Cabri. Our aim is to scrutinize the students’ reasoning, how the gap from perception to theory is filled, how Cabri influences the reasoning. We have singled out a sequence of phases in which the students pass from exploration to increasing degrees of formal reasoning. Our study reveals, among other things, that Cabri fosters the flexible use of methods close to analysis and synthesis.