Abstract
This article aims at presenting and testing some methodological tools for describing students’activities and its articulation with the teachers’one in a context of geometry lessons. The description relies on elementary logical analysis of mathematical concepts in order to anticipate the number and nature of objects that could be involved in students’activities. This then structures our three selected observables in a homogenous way, each of us being linked to one aspect of activity (material, visual and linguistic). In a first illustration, we deal with intrasubjective relationships between these three different aspects for a single student during the learning process then, in a second, with intersubjective relationships between two teachers’activities and their students’ ones.