**Definition of Congruent Triangles**

- Two triangles are said to be congruent if their corresponding sides and angles are equal.

**More about Congruent Triangles**

- The following congruency tests are used to check the congruency of two triangles:
- SAS Congruency Postulate: If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the two triangles are congruent.
- SSS Congruency Postulate: If three sides of one triangle are congruent to three sides of another triangle, then the two triangles are congruent.
- ASA Congruency Postulate: If two angles and the included side of one triangle are congruent to the two angles and the included side of another triangle, then the two triangles are congruent.
- SAA Congruency Postulate: If two angles and the non-included side of one triangle is congruent to two angles and the non-included side of another triangle, then the two triangles are congruent.

**Example of Congruent Triangles**

- Since all the sides and angles of the triangles ABC and MPN are equal, so triangle ABC is congruent to triangle MPN.

**Solved Example on Congruent Triangles**

ΔABC and ΔEDF are congruent triangles. Find the length of EF.

Choices:

A. 3 in.

B. 4 in.

C. 6 in.

D. 5 in.

Correct Answer: B

Solution:

Step 1:Congruent triangles have congruent corresponding parts (sides and angles).

Step 2:Length of EF = length of AC = 4 in.

**Related Terms for Congruent Triangles**

- ASA Congruency Postulate
- Congruent
- SAA Congruency Postulate
- SAS Congruency Postulate
- SSS Congruency Postulate
- Sides
- Triangle