There are six ways to judge congruent triangles * * *: side edge (SSS), corner edge (SAS), corner edge (ASA), corner edge (AAS), hypotenuse of right triangle and right edge (HL).

After flipping and translating, two triangles that can completely overlap are called congruent triangles, and the three sides and three angles of the two triangles are equal. Congruent triangles refers to two congruent triangles whose three sides and three angles are equal. Congruent triangles is one of congruences in geometry. According to congruence transformation, two congruent triangles are still congruence after translation, rotation and folding.

Judge:

SSS (Edge-Edge-Edge): A triangle with three equal sides is congruent triangles.

SAS (Edge-Angle-Edge): A triangle with two edges and an equal included angle is the congruent triangles.

ASA(Angle-Side-Angle): the coincidence of two angles, and their clamping edges correspond to equal triangles. ?

AAS(Angle-Angle-Side): Two angles and the opposite side of an angle correspond to the congruence of an equal triangle.

RHS (right angle-hypotenuse-edge) (also known as HL theorem (hypotenuse, hypotenuse-edge)): In a pair of right-angled triangles, the hypotenuse is equal to the other right-angled edge. (proved by SSS principle)

The following two items cannot be determined:

AAA(Angle-Angle-Angle): triangles are equal, which can not prove congruence, but can prove similar triangles.

SSA (Edge-Edge-Angle): An angle is equal, and two edges not included in the angle are equal.

Reference from: congruent triangles-Baidu Encyclopedia