Angles A and D will also be congruent, since all the angles of a triangle add up to 180. So if two corresponding pairs of angles in two triangles are congruent, then the third corresponding pair of angles will be congruent as well.

ASA can now be used to justify AAS triangle congruence.[br][br][list][*]Angle A is congruent to angle D[/*][*]Angle B is congruent to angle C[/*][*]AB = DE[/*][/list][br]Two pairs of corresponding angles and the included side are congruent, so the conditions for ASA are met.