Resumen

Diagrams and in general the use of visualization and manipulative material, play an important role in mathematics teaching and learning processes. Although several authors warn that mathematics objects should be distinguished from their possible material representations, the relations between these objects are still conflictive. In this paper, some theoretical tools from the onto-semiotic approach of mathematics knowledge are applied to analyse the diversity of objects and processes involved in mathematics activity, which is carried out using diagrammatic representations. This enables us to appreciate the synergic relations between ostensive and non-ostensive objects overlapping in mathematics practices. The onto-semiotic analysis is contextualised in a visual proof of the Pythagorean theorem.