Rigid transformations produce figures that are exactly the same shape and size. Here, you will learn what it means for two figures to be congruent. You will then focus on congruent triangles, and learn different ways to show that two triangles are congruent.
If rigid transformations can carry one figure to another, then the figures are congruent. You learned that to show that two triangles are congruent, you can verify that all corresponding angle and side pairs are congruent, or use one of the four of criteria for triangle congruence-AAS, ASA, SAS, SSS. You also learned a fifth criterion for triangle congruence that works for right triangles - HL. You learned how to use rigid transformations to explain the criteria for triangle congruence and you practiced identifying whether or not triangles are congruent.