1. Geometry 4.3 Using Congruent Triangles

2. In yesterday’s lesson you learned how to prove two triangles congruent by SSS SAS ASA After we prove Δ’s …….today we will prove segments or angles using CPCTC If 2 triangles are congruent All of their 6 corresponding parts are congruent

3. A Way to Prove Two Segments or Two Angles Congruent • Identify 2 triangles in which the 2 segments or angles are corresponding parts • Prove that the 2 triangles are congruent (use SSS, ASA, or SAS) • State that the 2 parts are congruent, using the reason CPCTC

4. Plan the Proof: Q Given: PR bisects QPS PQ PS Prove: Q S 7 1 P R 2 7 7 S Plan: 7 1 7 2 PQ PS PQ PS PR PR Δ PQR PSR by SAS, so Q S (CPCTC) Δ 7 7

5. Plan the Proof: Z Y Given: WX YZ ZW XY Prove: WX ZY 2 3 4 1 W X Plan: WX YZ ZW XY ZX ZX Δ ZWX XYZ by SSS, so 12 (CPCTC), so WX ZY because Alt Int. <‘s lines Δ 7 7

6. Lines to a Plane A Given: M is the midpoint of AB plane X AB at M P M X What can you deduce about AP and BP ? Plan: Δ APM Δ BPM by SAS so AP BP (CPCTC) B

7. Let’s try a few from the HW Please open your books to page 130 #2 and #4

8. Homework pg. 130 # 1 - 8