Although in two congruent triangles each side of one must be equal in size to each corresponding side of the other, and each angle of one must be equal in measure to its corresponding angle, it is not necessary to prove that in order to prove two triangles congruent. Several postulates follow that name minimum conditions for two triangles to be congruent:

Angle-Angle-Side (AAS) Postulate
If two angles of one triangle and a side not between them are congruent to the corresponding parts of a second triangle, them the two triangles are congruent.