# AAS, HA, LL and HL Theorems

If two angles of one triangle are congruent to two angles in another triangle then the third angle of the first triangle is congruent to the third angle of the second triangle.

So when we need to prove that two triangles are congruent and we have two pairs of congruent angles and a pair of congruent sides then we can use the triangle angle sum theorem to prove the third pair of angles is congruent; thus using the ASA Postulate the two triangles are congruent

Since the above argument is always true then the following theorem can be used to prove that two triangles are congruent.

Find out more about AAS, HA, LL and HL theorems by reading the explanation below.

**Practice:** Answer the following exercises about AAS, HA, LL and HL theorems.