Lesson 2 - Congruence and Similarity After we learned about the properties of one triangle, in Lesson 2, we went on to learn about the properties of comparing and proving the congruence of two triangles. The properties in this lesson came mainly in the form of postulates. Further down the road, these postulates would greatly benefit me when I wrote proofs, for they would serve as excellent reasons when proving the congruence between two triangles. Some of these postulates include the SAS Postulate, SSS Postulate, AAS Postulate, ASA Postulate, and the HL Postulate.