The congruence theorem is ASA.If you look at the diagram, angle X and angle Z are both right angles, or 90 degrees. This means that these two angles are congruent. Then, segment SZ and segment SX have that line in them, which means that they are congruent. Finally, angle WSX and angle YSZ are vertical angles, meaning that they are also congruent. Since the segments SZ and SX are between the two congruent angles of the triangles, the theorem is ASA.
