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Lesson 1.2 Use segments and congruence Objective • Use segment postulates to identify congruent segments. Standard • 1.0 – Students demonstrate understanding by identifying and giving examples of undefined terms, axioms, theorems, and inductive and deductive reasoning. Academic Language Postulate or axiom • A rule that is accepted without proof Postulate 1 • The points on a line can be matched one to one with real numbers Coordinate • the real number that corresponds to a point Points A B X1 X2 Coordinates Distance • The absolute value of the difference of 2 points A and B, written as AB A AB X1 B X2 AB x2 x1 Example 1 What is the distance between points S and T? S T 2 5.4 Indy Practice What is the distance between points A and B? A B -4 7 Adding Segment Lengths • When 3 points are collinear, you can say that one point is between the other two. Example A D B C E F Which point is between? Why? Postulate 2 – Segment addition Postulate • If B is between A and C, then AB + BC = AC • If AB + BC = AC, then B is between A and C AC A B AB C BC The Real World • The cities Lubbock, Tulsa, and St. Louis lie approximately in a straight line on a map. Tulsa is between Lubbock and St. Louis, 380 miles from Lubbock and 360 miles from St. Louis. Find the distance from Lubbock, Texas to St. Louis, Missouri Indy Practice 1. Find the length of XZ 2. WY = 30. Can you use segment addition to find the distance between W and Z? Explain 23 X 50 Y W Z More Practice • Find GH 36 F 21 G H Congruent Segments • Line segments that have the same length Example • Plot J(-3, 4) K(2, 4) L(1, 3) M(1, -2) Congruent? Homework • p.12 #1, 2, 3, 11, 13, 17, 21, 29, 33