stereometry, prototype, mistake, misconcept

The paper focuses on detecting a tendency of students to have a prototypical thought in stereometry and consequences for mathematical thinking in geometry. The summary of the results obtained by questionnaires given to selected high schools are described. It mainly concerns the fact if the way used by students to sketch the specified units is similar to what they may have seen in the textbooks, eventually to results of their teachers, or if it depends on, for example, left-right orientation, sex, age or type of studied school. In addition, a proposal will be outlined on how to innovate the teaching of mathematics in order to develop students' prototypical thinking.