2 Find Angle Measures in a Triangle Property The Sum of the Angle Measures in a Triangle The measures of the angles in a triangle add up to 180. Example: a b c ma mb mc 180 We can use this fact to fi nd missing angle measures in a triangle. Find mx in each triangle. a) x 21° 33° Solution a) Since the measures of all the angles in a triangle add up to 180, we fi nd mx by subtracting: mx 180 33 21 126 b) It may look like only one angle is labeled (37), but remember that the angle marked with the small square is a right angle, so its measure is 90. All of the EXAMPLE 4 Find 90 37. How could that help you with triangles that have a right angle? YOU TRY 4 Find mx in each triangle. a) x 39° 74° mx 180 37 90 53 b) b) x The measure of the right angle x angles add to 180. 65° 37° 312 CHAPTER 4 Basic Geometry Concepts and Algebra www.mhhe.com/messersmith
messersmith_power_prealgebra_1e_ch4_7_10
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