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Quarter 4 for Dummies Sect. 13.3 Finding reference angles. Audrey Graves and Colton Brown. What is a reference angle?. A reference angle is an acute angle formed by terminal side and the x-axis denoted by Theta Prime. ( ϴ ’). ϴ. ϴ ’. 90 ° to 180 °.
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Quarter 4 for DummiesSect. 13.3Finding reference angles Audrey Graves and Colton Brown
What is a reference angle? • A reference angle is an acute angle formed by terminal side and the x-axis denoted by Theta Prime. (ϴ’) ϴ ϴ’
90° to 180° • If your original angle is between 90 degrees and 180 degrees, you take your original angle and subtract that from 180 degrees. DEGREESRADIANS ϴ =90° to 180°π/2 to π ϴ’= 180°- ϴπ+ ϴ
Example • Find ϴ’ if ϴ = 120° 180° - 120° = 60° = ϴ’(you will always have an acute angle) • Find ϴ’ if ϴ = 2π/3 π - 2π/3 = π/3 = ϴ’(if your problems are given to you in radians you must give the answer in radians)
180° to 270° • If your original angle is between 180° and 270°, you subtract 180° from your original angle. DEGREESRADIANS ϴ =180° to 270°πto 3π/2 ϴ’= ϴ - 180°ϴ - π
Example • Find ϴ’ if ϴ = 210° 210° - 180° = 30°= ϴ’ • Find ϴ’ if ϴ = 7π/6 7π/6 - π = π/6 = ϴ’
270° to 360° • If the original angle is between 270° to 360°, take 360° minus your original angle. DEGREESRADIANS ϴ =270° to 360° 3π/2 to 2π ϴ’=360° - ϴ2π - ϴ
Example • Find ϴ’ if ϴ = 300° 360° - 300° = 60° = ϴ’ • Find ϴ’ if ϴ = 5π/3 2π - 5π/3 = π/3 = ϴ’