Here are the key points in the example:
1. The triangles ΔCAT and ΔDOG are placed on top of each other so that their vertices coincide or overlap.
2. This establishes a correspondence between the parts of the two triangles.
3. Since the vertices coincide, the corresponding sides and angles also coincide.
4. Triangles with coinciding corresponding parts are said to be congruent.
5. The congruence of the two triangles is symbolized as ΔCAT ≅ ΔDOG.