Investigation of preservice mathematics teachers' content knowledge on congruence and similarity of triangles

This study investigates the content knowledge of prospective mathematics teachers concerning the concepts of congruence and similarity in triangles.The research was conducted during the 2023–2024 academic year with first-, second-, third-, and fourth-year students enrolled in the Mathematics Education and Elementary Mathematics Education departments at a public university.An activity sheet comprising six questions was developed for the study. This sheet included two congruence theorems, one congruence postulate, two similarity theorems, and one similarity postulate. The data were collected from a total of 188 prospective teachers and analyzed accordingly. The results of the content analysis revealed that prospective teachers had significant deficiencies in their understanding of triangle congruence and similarity. Although a majority of the participants were able to solve problems using congruence and similarity rules between triangles, they often did so without explicitly stating which congruence or similarity postulate/theorem they were applying. Furthermore, it was observed that they generally did not provide adequate explanations and failed to use mathematical language effectively.Based on these findings, it is recommended that similar research be conducted with in-service elementary and secondary mathematics teachers.