140 likes | 284 Views
2.6 Prove Statements About Segments and Angles. Objectives. Write proofs involving segment and angle addition Write proofs involving segment and angle congruence. Two-Column Proof. Recall what a two-column proof was…
E N D
Objectives • Write proofs involving segment and angle addition • Write proofs involving segment and angle congruence
Two-Column Proof Recall what a two-column proof was… • Two-Column Proof – A proof format used in geometry in which an argument is presented with two columns, statementsand reasons, to prove conjectures and theorems are true. Also referred to as a formal proof.
Proof: Statements Reasons Two-Column Proof
Prove the following. Given: PR = QS Prove: PQ = RS Proof: Statements Reasons 1. 1. Given PR = QS 2. 2. Subtraction Property PR – QR = QS – QR 3. 3. Segment Addition Postulate PR – QR = PQ; QS – QR = RS 4. 4. Substitution PQ = RS Example 1:
Prove the following. Given: Prove: Your Turn:
Proof: Statements Reasons 1. 1. Given AC = AB, AB = BX 2. 2. Transitive Property AC = BX CY = XD 3. 3. Given 4. AC + CY = BX + XD 4. Addition Property 5. 5. Segment Addition Property AC + CY = AY; BX + XD = BD 6. 6. Substitution AY = BD Your Turn:
Congruence of Segments Theorem 2.1 (Congruence of Segments) Congruence of segments is reflexive, symmetric, and transitive. Reflexive Property: AB AB Symmetric Property: If AB CD, then CD AB. Transitive Property: If AB CD and CD EF, then AB EF.
Congruence of Angles Theorem 2.2 (Congruence of Angles) Congruence of angles is reflexive, symmetric, and transitive. Reflexive Property:A A Symmetric Property: If A B , then B A Transitive Property: If A B and B C , then A C .
Prove the following. Given: Prove: Example 2:
Proof: Statements Reasons 1. Given 1. 2. Definition of congruent segments 2. 3. 3. Given 4. Transitive Property 4. 5. Transitive Property 5. Example 2:
Prove the following. Given: Prove: Your Turn:
Statements Reasons 1. 1. Given 2. 2. Transitive Property 3. 3. Given 4. 4. Transitive Property 5. 5. Symmetric Property Your Turn: Proof:
Assignment • Geometry: Pg. 116 – 119 #3 – 13, 16, 21, 22