Preservice teacher proficiency with transformations-based congruence proofs after a college proof-based geometry class

This report explores pre-service teachers' proficiency with concepts of transformational geometry at the end of a semester-long advanced geometry course. In the course, the instructor incorporated transformational geometry content, including congruence proofs, in an attempt to prepare the pre-service teachers to teach high school geometry in alignment with the Common Core State Standards for Mathematics. At the conclusion of the course, students expressed a preference for using traditional triangle congruence criteria (SAS, ASA, SSS, and AAS) over using transformations to complete proofs, but were nevertheless generally successful in completing proofs using transformations. Similarly, while the students often described thinking of transformations in terms of analytic forms, they were successfully able to prove triangle congruences in synthetic contexts. Finally, some evidence indicates that students may have motion or process conceptions of transformations, but not map or object conceptions, but this evidence is not conclusive.