Analysis of the Relationship between Similarity Issues in Geometry and Task Modification: Focusing on Secondary Pre-service Teachers' Strategies for Solving Type 1 Dilemmas

Task modification ability is essential for developing mathematics teachers' professional expertise. This study analyzed the relationship between secondary pre-service teachers' understanding of geometric similarity and their task modification strategies, exploring strategies for resolving first-type definition dilemmas. Twenty pre-service teachers from a teachers' college in Chungcheongbuk-do modified middle school geometric similarity tasks. Results showed teachers primarily used question, system, and example modifications, with many attempting first-type dilemma resolution. Teachers with higher similarity understanding employed diverse modification types and higher cognitive effort levels, while those with lower understanding relied on limited modifications. This study highlights the need for integrated approaches to conceptual understanding and task modification strategies in pre-service teacher education.