Designing dynamic geometry tasks that support the proving process

A major challenge for mathematics education is to find ways in which proof in geometry has communicatory, exploratory, and explanatory functions alongside those of justification and verification. Ongoing research is suggesting that providing students with tasks which state “prove that…” might actually inhibit students’ capacity for proving. In contrast, open tasks which favour a dynamic exploration of a statement and encourage the use of transformational reasoning may allow students to reconstruct, in terms of properties and relationships, all the elements needed in the proof. In this report we consider the transforming of closed problem into open ones and discuss the use of dynamic geometry software, such as Cabri, in such a process