4.2 Triangle Congruence by SSS and SAS

• You can prove that two triangles are congruent without having to show that all corresponding parts are congruent.– You will prove triangles congruent by using:

• Three pairs of corresponding sides.• Two pairs of corresponding sides and one pair of

corresponding angles.

Side-Side-Side• If the three sides of one triangle are congruent to three

sides of another triangle, then the two triangles are congruent.

Side-Angle-Side• 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.

Included Angle

Using SAS• What other information do you need to prove that

triangle DEF is congruent to triangle FGD by SAS? Explain.

• Diagram shows that segment EF is congruent to segment GD.

• Segment DF is congruent to segment DF.• You need to know that angle EFD is congruent to angle

GDF.

Identifying Congruent Triangles• Would you use SSS or SAS to prove the triangles

congruent? If there is not enough information to prove the triangles congruent SSS or SAS, write not enough information. Explain your answer.

More Practice!!!!!

• Homework – Textbook p. 231 #11 – 14, 18 – 20, p. 232 # 24 – 26.