Similarity and Congruence
Lecture no. 9 from the course: Geometry: An Interactive Journey to Mastery
Taught by Professor James Tanton | 33 min | Categories: The Great Courses Plus Online Mathematics Courses
Define what it means for polygons to be “similar” or “congruent” by thinking about photocopies. Then use that to prove the third key assumption of geometry—the side-angle-side postulate—which lets you verify when triangles are similar. Thales of Ionia used this principle in 600 B.C.E. to impress the Egyptians by calculating the height of the pyramids.