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