Norms That Regulate the Theorem Construction Process in an Inquiry Classroom of 3D Geometry: Teacher's Management to Promote Them

This paper aims to illustrate how a teacher instilled norms that regulate the theorem construction process in a three-dimensional geometry course. The course was part of a preservice mathematics teacher program, and it was characterized by promoting inquiry and argumentation. We analyze class excerpts in which students address tasks that require formulating conjectures, that emerge as a solution to a problem and proving such conjectures, and the teacher leads whole-class activities where students' productions are exposed. For this, we used elements of the didactical analysis proposed by the onto-semiotic approach and Toulmin's model for argumentation. The teacher's professional actions that promoted reiterative actions in students' mathematical practices were identified; we illustrate how these professional actions impelled students' actions to become norms concerning issues about the legitimacy of different types of arguments (e.g., analogical and abductive) in the theorem construction process.