Improving the learning of geometric proportionality using van Hiele’s model, mathematical visualization, and GeoGebra

This qualitative, action research methodology study aims at the construction of a teaching unit for development learning processes, analyzing trajectories students around geometric proportionality in topics related to similarity, homothecy, and Thales’ theorem. The didactic was designed under principles phases van Hiele’s (1986) model, mathematical visualization, use GeoGebra software. Among results obtained, it can be evidenced that went from not having clear notion similarity constructing definition proportionality, homothecy; identifying criteria understanding properties remain invariant similar figures; using visualization skills communicating their arguments an appropriate language processes.