Lesson 4-4 Proving Triangles Congruent-SSS and SAS

Vocabulary Included angle-The Angle formed by two adjacent sides of a polygon.

Concept 1

Example 1 Use SSS to Prove Triangles Congruent Prove:ΔQUD  ΔADU Given:QU  AD, QD  AU ___

Example 1 CYP Which information is missing from the flowproof? Given:AC  AB D is the midpoint of BC. Prove:ΔADC  ΔADB ___ A.AC  AC B.AB  AB C.AD  AD D.CB  BC ___

Concept 2

Example 3 Use SAS to Prove Triangles are Congruent ENTOMOLOGY The wings of one type of moth form two triangles. Write a two-column proof to prove that ΔFEG  ΔHIG if EI  FH, and G is the midpoint of both EI and FH.

Example 3 A.ReflexiveB. Symmetric C.TransitiveD. Substitution 3. SSS 3. ΔABG ΔCGB 2. ? Property Reasons Proof: Statements 1. Given The two-column proof is shown to prove that ΔABG  ΔCGB if  ABG   CGB and AB  CG. Choose the best reason to fill in the blank.