2. 10/20/2011Keystone Geometry Proving Parts of Triangles using CPCTC

3. Proof Format When using CPCTC to prove that corresponding parts of a triangle are congruent, we use the same general format: –Determine the 3 pieces of congruency based on the given information and the diagram –Determine what the two congruent triangles are and the method of congruence –Use CPCTC to prove the corresponding parts. When using CPCTC to prove that corresponding parts of a triangle are congruent, we use the same general format: –Determine the 3 pieces of congruency based on the given information and the diagram –Determine what the two congruent triangles are and the method of congruence –Use CPCTC to prove the corresponding parts.

4. Complete the following proof: StatementsReasons 1.DF bisects <EDG DE = DG 2. <1 = <2 3. DF = DF 4. ∆ = ∆ 5.

5. Complete the following proof: StatementsReasons 1. PR=SR; PQ=SQ1. Given 2. QR=QR2. Reflexive 3. ∆PQR= ∆SQR3. SSS Postulate 4. <P=<S4. CPCTC

6. Complete the following proof: StatementsReasons 1. C is the midpoint of AD; <A=<D 1. Given 2. AC=CD2. Def. of a Midpt. 3. <ACB=<DCE3. Vertical Angles 4. ∆ABC= ∆DEC4. ASA Postulate 5. BC=EC5. CPCTC

7. Complete the following proof: StatementsReasons 1. WY is perp. To XZ; XY=YZ 1. Given 2. <XYW=<ZYW2. If 2 lines are perp. Then they form = adj. <s 3. WY=WY3. Reflexive 4. ∆XYW= ∆ZYW4. SAS Postulate 5. <X=<Z5. CPCTC