3.To find:
The right angle congruence theorem is used to prove that two triangles are congruent.
Solution:
In the given triangles, the corresponding hypotenuse and the corresponding angle are equal. So, the congruence used here is the Hypotenuse-Angle congruence that implies ABC is congruent to DEF.
Thus, the answer is Hypotenuse-Angle congruence.
