Drawing in movement and insights for the proof process

The understanding of the cognitive abilities that produces the student's transition from empirical arguments to deductive arguments is one of main research areas in the learning of geometry. By using dynamical geometry environments, students show progress in the production of their own proofs, although great part of their final proofs is based on static drawings. The central concern of this article is about dynamical visual proofs, which are based on 'drawing in movement' that can be properly performed in a dynamical environment. The interactions of students with this dynamical feature, in a long-term use, can produce the development of cognitive abilities towards dynamical visual proofs. This article concentrates in two dynamical visual proofs, produced by students in pre-service programme for mathematics teachers.