Introduction to Proof: The Mediation of a Dynamic Software Environment

This paper, which reports on a long-term teaching experiment carried out in the 9^th and 10^th grades of a scientific highschool, is part of a larger co-ordinated research project. The workconstitutes a `research for innovation', in which action in the classroom isboth a means and result of a study aimed at introducing pupils totheoretical thinking and at studying the ways in which this process isrealised.The purpose of the study is to clarify the role of a particular software,Cabri-géomètre, in the teaching/learning process. Assuming aVygotskian perspective, attention is focussed on the social construction ofknowledge and on the semiotic mediation accomplished through culturalartefacts; the functioning of specific elements of the software will bedescribed and analysed as instruments of semiotic mediation used by theteacher in classroom activities.