Unit 3, Lesson 13# Proof of the Pythagorean Theorem

EngageNY 45 min(s)

Students practice applying the Pythagorean theorem to find the lengths of sides of right triangles in two dimensions. The following proof of the Pythagorean theorem is based on the fact that similarity is transitive. Once it is shown that all three triangles are in fact similar, comparing the ratios of corresponding side lengths proves the theorem. Therefore, it may be beneficial to do this proof simultaneously with triangles that have concrete numbers for side lengths.