Final answer:
The SS (Side-Side) theorem can be used to prove that two triangles are congruent, whereas the Pythagorean theorem is used to find the length of a side in a right triangle.
Step-by-step explanation:
The theorem that can be used to prove that two triangles are congruent is the SS (Side-Side) theorem. According to this theorem, if two sides of a triangle are congruent to two sides of another triangle, and the included angles are congruent, then the two triangles are congruent.
For example, if triangle ABC and triangle XYZ have AB = XY, BC = YZ, and ∠A = ∠X, then we can conclude that triangle ABC is congruent to triangle XYZ.
The Pythagorean theorem, which states that in a right triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides, is not used to prove congruence, but to find the length of a side in a right triangle.