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A Follow-Up of Lesson 9-8 Finding Angles of a Right Triangle A TI-82 calculator can be used to find the measure of an acute angle of a right triangle if you know the measures of two sides of the triangle. Example The end of an exit ramp from an interstate highway is 22 feet higher than the highway. If the ramp is 630 feet long, what angle does it make with the highway? 630 ft x˚ 22 ft A Determine which trigonometric ratio is needed to solve the problem. Since you know the measure of the leg opposite ⬔A and the hypotenuse, use the sine ratio. Write the ratio. opposite hypotenuse sin ⬔A ⫽ ᎏᎏ Sine Ratio 22 630 sin ⬔A ⫽ ᎏᎏ Substitution Use a calculator to find the measure of ⬔A. The SIN⫺1 function will find the angle measure, given the value of its sine. Be sure that your 2nd [SIN⫺1] ( 22 ⫼ 630 ) ENTER 2.001211869 calculator is in degree To the nearest degree, the measure of ⬔A is 2°. mode. Exercises Use a calculator to find the measure of each acute angle. Round to the nearest degree. 1. 2. B F E 13.5 ft 7 ft 17 m A D 39 m C m⬔B ⬇ 59°; m⬔C ⬇ 31° m⬔F ⬇ 26°; m⬔D ⬇ 64° 3. A flower garden is located 46 meters due west of an elm tree. A fountain is located 19 meters due south of the same elm tree. What are the measures of the angles formed by these three park features? 22°, 68°, 90° www.pre-alg.com/other_calculator_keystrokes 482 Investigating Slope-Intercept Form 482 Chapter 9 Real Numbers and Right Triangles TI-82