Mathematics teacher’s specialized knowledge (mtsk) in the “dissecting an equilateral triangle” problem

This paper focuses on describing a model for the analysis of the mathematics teachers’ knowledge from the perspective of what is peculiar to teaching mathematics, and gives an example of its application to the knowledge deployed by a teacher during a lesson. We first present the analytical model, the MTSK (mathematics teacher’s specialized knowledge) model, developed at the University of Huelva (Spain), and then demonstrate its potential in the case of a high school teacher working through a problem with her students. We conclude with a summary of the advantages the model offers in detailing the elements of specialized knowledge displayed by the teacher, and illustrate how this knowledge enables her to plan highly productive learning opportunities for her students. A final reflection notes the potential of the MTSK model as a tool for teacher training