Step 1: Remember the AAA congruent theorem
DEFINITION: In two triangles, if the angles are equal, then the sides
opposite to the equal angles are in the same ratio (or proportional) and
hence the two triangles are similar.
Step 2: Find the two triangles with three pairs of congruent angles.
EXAMPLE: \angle P = \angle L
\angle Q = \angle M
\angle R = \angle N
Step 3: Conclude that the given triangles are congruent if the two triangles with
three pairs of congruent angles.
EXAMPLE: three angles of △PQR are congruent to three angles
of △LMN, so these triangles are congruent by the AAA Theorem.