Resumen

This article highlights the details of an ongoing professional development study in the area of mathematics teacher education; with particular attention to mathematics teachers' constructions and sense-making of a variety of circle theorems involving arcs, segments, chords, tangents, and secants using GeoGebra dynamic geometry software. One of the main findings is that mathematics teachers visualized the circle theorems via constructions mostly of well-behaved (appropriately constrained) nature, although there were instantiations of premature constructions at times. Whereas teachers were successful in demonstrating and justifying the visual proofs of circle theorems on the dynamic geometry software, confirmation of these visualizations via analytical approaches proved challenging.