How to generalize Thales’ Theorem?

Sa？etak The classical theorem of Thales can be generalized – depending on someones interpretation – in several elemental or abstract ways. This paper tries to classify such generalizations without claim of completeness. We structured this work in a way that is suitable for educational purposes by emphasizing aspects of mathematical research. Beside more or less known facts, we present new insights and approaches to one of the most important theorems of geometry