Abstract When analyzing the relationships between knowledge and the teacher, some relationships related to the planning of teaching practices during professional practice are identified. One of the known reasons for these knowledge needs in planning is the lack of recognition of other elements in school mathematics. Under the theoretical perspective of the model of the specialized knowledge of the teacher who teaches mathematics, this qualitative research aims to characterize the elements of specialized knowledge in a geometry class and the subsequent reflection of the tasks of planning teaching. Among the main results of this research show the need to deepen the knowledge of the “basic” concepts of geometry, such as the cube, its characteristics and its representation from different perspectives. Therefore, it is necessary to motivate in teachers the need to develop their own spatial visualization skills, so that they apply them to the school mathematics they teach in their daily lives.