Chapter 1 Basics of Geometry Section 5 Segments

Chapter 1 Basics of Geometry

Section 5 Segments and Their Measures

The points on a line can be matched one to one with the real numbers. The real number that corresponds to a point is the coordinate of the points. In the diagram, x 1 and x 2 are coordinates. The small numbers are subscripts. The coordinates are read as “x sub 1” and “x sub 2”. The distance between points A and B is written as AB. It is the absolute value of the difference of the coordinates of A and B. AB is also called the length of AB.

Example 1: Find the Distance Between Two Points Measure the total length of the shark’s tooth to the nearest 1/8 inch. Then measure the length of the exposed part.

Checkpoint: Find the Distance Between Two Points Measure the length of the segment to the nearest 1/8 inch.

When three points lie on a line, one of them is between the other two. In the diagram of Postulate 5 below, B is between A and C.

Example 2: Find a Distance by Adding Use the map to find the distance from Athens to Albany.

Example 3: Find a Distance by Subtracting Use the diagram to find EF.

Checkpoint: Use the Segment Addition Postulate Find the length.

Congruence In geometry, segments that have the same length are called _______________.

Example 4: Decide Whether Segments are Congruent Are the segments shown in the coordinate plane congruent?

Checkpoint: Decide Whether Segments are Congruent Plot the points in a coordinate plane. Then decide whether AB and CD are congruent. 1. A (-2, 3), B(3, 3), C(-3, 4), D(-3, -1) 2. A(0, 5), B(0, -1), C(5, 0), D(-1, 0)