In the last decade the introduction of technology into the curriculum has been of great concern to education researchers , thought as a link between mathematics and technology. In this document a part of the group's work EDUMAT research is concerned with the teaching of geometry , more precisely the axial symmetry using dynamic geometry software CABRI presented . a-posteriori analysis of two activities designed in advance and implemented to seventh graders (12-13 years ) is presented . The theory of didactic situations gives us the conceptual tools with which we address both the a-priori analysis and design and implementation and a-posteriori analysis of the proposed activities .