The Learning and Teaching Geometry project (LTG) creates five video case modules for use in professional development of middle school mathematics teachers. The materials are designed to develop teachers' understanding of mathematics knowledge for teaching similarity. Module I, the foundation module, focuses on a thorough grounding of similarity and contains 6-8 video case sessions. The four extension modules offer options for further exploration: (1) Definitions and Theorems; (2) The Role of Language in Geometry; (3) Choosing and Using Technological Tools; and (4) Bridging to High School Geometry. In total, 18-24 video cases are produced, which, taken together, form the curriculum of a 45 to 60-hour professional development course.
