Exercise 4 Page 625

As long as we have enough information about two triangles, we can use any theorems that require those pieces of information. Let's draw two triangles and include some information about their angles and sides.

In this situation we could, for example, use the Angle-Angle Side (AAS) Congruence Theorem to prove congruence between $△ABC$ and $△DEF.$ This theorem requires us to know two angles and the included side.

However, we could also use the Angle-Side-Angle (ASA) Congruence Theorem. This requires us to know two sides and the included angle.