Definition 1) An acute angle is an angle whose measure is greater than 0 and less than 90. Examples: 45° 72° 18° 2) A right angle is an angle whose measure is 90. Examples: 90° 90° 90° 3) An obtuse angle is an angle whose measure is greater than 90 and less than 180. Examples: 120° 157° 94° 4) A straight angle is an angle whose measure is 180. Examples: 180° 180° Note Angles can also be measured in radians. This topic is studied in future math courses. Classify each angle as acute, right, obtuse, or straight. a) P Q R b) A B C c) Y d) X Z T Solution a) The measure of PQR is greater than 90 and less than 180. It is an obtuse angle. b) The small square inside the angle tells us that its measure is exactly 90. ABC is a right angle. c) The measure of YXZ is less than 90, so it is an acute angle. d) The measure of T is 180, so it is a straight angle. EXAMPLE 3 288 CHAPTER 4 Basic Geometry Concepts and Algebra www.mhhe.com/messersmith
messersmith_power_prealgebra_1e_ch4_7_10
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