摘要：In this article, we focus on a priori analysis as a part of teacher’s lesson planning. We show a concrete use of this analysis during a posteriori analysis of a lesson (analysis after lessons) and describes its importance in teachers’ work. We chose a problem from geometry, which was solved by secondary school students. The goal of the article is to point out the importance of a priori and also a posteriori analysis for teachers from the point of view of the theory of didactic situations.
