Talli Nachlieli, Patricio Herbst and Gloriana González

July 2009, Volume 40, Issue 4, Pages 427 - 459

Abstract:
This article reports on an investigation of how teachers of geometry perceived an episode of instruction presented to them as a case of engaging students in proving. Confirming what was hypothesized, participants found it remarkable that a teacher would allow a student to make an assumption while proving. But they perceived this episode in various ways, casting the episode as one of as many as 10 different stories. Those different castings of the episode make use of intellectual resources for professional practice that practitioners could use to negotiate the norms of a situation in which they had made a tactical but problematic move.

Classification:
Geometry (see also Measurement)
Reasoning
Proof
Teachers
Teaching

Additional Keywords:
Classroom interaction; Decision-making; Linguistics; Proof in geometry; Teacher beliefs; Teaching practice