What else must you know to prove the triangles congruent by SAS?
In addition to the Side-Angle-Side (SAS) congruence criterion, you must know the following:
1. The lengths of the two sides that form the sides of the triangle you are comparing. These sides must be of equal length in both triangles.
2. The measure of the angle formed by the two congruent sides in both triangles. This angle must be of equal measure in both triangles.
With these pieces of information, you can use the SAS congruence criterion to prove that the two triangles are congruent.