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Chapter 2.7. Proving Segment Relationships. Objective: Practice using proofs for geometric relationships by starting with segments. Geometric Properties . Add to your listing. Postulate 2.8 (Ruler Postulate)
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Chapter 2.7 Proving Segment Relationships Objective: Practice using proofs for geometric relationships by starting with segments
Geometric Properties Add to your listing • Postulate 2.8 (Ruler Postulate) • The points on any line or line segment can be paired with real numbers so that given any two points A and B on a line, A corresponds to zeros and B corresponds to a positive real number. • Postulate 2.9 (Segment Addition Postulate) • If B is between A and C, then AB + BC = AC or • If AB + BC = AC, then B is between A and C • Theorem 2.2 • Congruence of segments is reflexive, symmetric, and transitive. AB BC A B C AC It's not what you look at that matters, it's what you see. Henry David Thoreau
Use paper to solve • Given BC = DE • Prove AB + DE = AC • Statements • Reasons • BC = DE • AB + BC = AC • AB + DE = AC • Given • Segment Addition Postulate • Substitution
Use paper to solve P Q S R • Given PR QS • Prove PQ RS • Statements • Reasons • PR QS • PR = QS • PQ + QR = PR • QR + RS = QS • PQ + QR = QR + RS • PQ = RS • PQ RS Given Definition of Congruence Segment Addition Postulate Segment Addition Postulate Substitution Subtraction Definition of Congruence
Proof with Segment Addition process Statements Reasons Given Addition Property Segment Addition Postulate Substitution PQ = RS PQ + QR = QR + RS PQ + QR = PR and QR + RS = QS PR = QS Prove the following: Given: PQ = RS Prove: PR = QS P Q S R
Proof with Segment Addition process Statements Reasons Given Subtraction Property Segment Addition Postulate Substitution PR = QS PR - QR = QS - QR PR - QR = PQ and QS - QR = RS PQ = RS Prove the following: Given: PR = QS Prove: PQ = RS P Q S R
Proof with Segment Congruence process Statements Reasons Given Transitive Property Given Transitive Property Symmetric Property JK KL, KL HJ JK HJ HJ GH JK GH GH JK J Prove the following: Given: JK KL, HJ GH, KL HJ Prove: GH JK L K H G
Prove the following. Which reason correctly completes the proof? Proof: Given:AC = ABAB = BXCY = XDProve:AY = BD 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. ________________ AC + CY = AY; BX + XD = BD 6. 6. Substitution AY = BD Segment Addition Postulate
Practice Assignment • Page 145, 4-16 even