To prove congruence using the SSS Congruence Theorem, we need to know that all corresponding sides of two triangles are congruent. From the diagram, we see that we have no information about the third side of the triangles. Therefore, to use the theorem, we would also need to know that AB ≅ CD.
b According to the HL Congruence Theorem, if the hypotenuse and a leg of a right triangle are congruent to the hypotenuse and a leg of a second right triangle, then the two triangles are congruent. Therefore, we would also need to know that the two triangles are right triangles.
