# 4-1 Congruent Figures - PC\|MAC 4-1 Congruent Figures 4-2 Triangle Congruence by SSS and SAS Congruent Polygons

Polygons that have congruent corresponding parts they have matching sides and angles. When you name congruent polygons, you must list corresponding vertices in the same order.

ORDER MATTERS!!! Congruent Triangles A B

D C A D

B F C E E F

AB DF BC FE AC DE Corresponding

Parts Example Write six things that are congruent if: Answers:

X C Y B Z A XY CB

YZ BA XZ CA Theorem 4-1: Third Angles Theorem All we need is to show 3 pairs of Corresponding Sides are

congruent in order to prove Triangle Congruence. Lets look at a couple of two-column proofs that utilize the SSS Postulate. Example 1:Using SSS

Given BD BD Reflexive Property SSS Postulate

Try Another Proof! SAS Postulate Example 2: Using SAS

We Know SK KS, because of the Reflexive Property. We need to know RSK TKS in order to use SAS to prove the triangles congruent Ex 2B: Using SAS

Example 3: Are the Triangles Congruent? Ex 3B: Are the Triangles Congruent?

Apply: Are these Triangles Congruent? If congruent say why, if not explain what else you would need to know to prove them congruent by SSS or SAS.

Apply: Are these Triangles Congruent? If congruent say why, if not explain what else you would need to know to prove them congruent by SSS or SAS.

Practice Proofs! More Proofs!