YOU TRY 3 Classify each angle as acute, right, obtuse, or straight. a) K b) R S c) Y Z d) T A Note The measure of an angle is denoted by m. For example, in Example 3b, the measure of ABC is 90. We write this as mABC 90. 3 Identify Parallel and Perpendicular Lines At the beginning of this section, we said that a plane is a fl at surface that continues indefi nitely. A surface like a piece of paper is part of a plane. Two lines that cross each other are called intersecting lines. A k l Lines l and k intersect at point A. Parallel lines are lines in the same plane that do not intersect. The symbol 7 means “is parallel to.” Lines x and y do not intersect. They are parallel. We can write x 7 y. Perpendicular lines intersect at right angles. The symbol means “is perpendicular to.” · Lines PQ R T · P and RT x y Q intersect at right angles. They are perpendicular. We · can write PQ · RT . www.mhhe.com/messersmith SECTION 4.1 Introduction to Geometry 289
messersmith_power_prealgebra_1e_ch4_7_10
To see the actual publication please follow the link above