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3.1 Reference Angle. A reference angle for an angle is the positive acute angle made by the terminal side of angle and the x -axis. a) 218 Positive acute angle made by the terminal side of the angle and the x -axis is 218 180 = 38. 1387
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3.1 Reference Angle • A reference angle for an angle is the positive acute angle made by the terminal side of angle and the x-axis.
a) 218 Positive acute angle made by the terminal side of the angle and the x-axis is 218 180 = 38. 1387 Divide 1387 by 360 to get a quotient of about 3.9. Begin by subtracting 360 three times. 1387 – 3(360) = 307. The reference angle for 307 is 360 – 307 = 53 Example: Find the reference angle for each angle.
Find the values of the trigonometric functions for 210. Reference angle: 210 – 180 = 30 Choose point P on the terminal side of the angle so the distance from the origin to P is 2. Example: Finding Trigonometric Function Values of a Quadrant Angle
An angle with its vertex at the center of a circle that intercepts an arc on the circle equal in length to the radius of the circle has a measure of 1radian. 3.2 Radians and Degrees
Converting Between Degrees and Radians • 1. Multiply a degree measure by radian and simplify to convert to radians. • 2. Multiply a radian measure by and simplify to convert to degrees.
Example: Degrees to Radians • Convert each degree measure to radians. • a) 60 • b) 221.7
Example: Radians to Degrees • Convert each radian measure to degrees. • a) • b) 3.25
Degrees Radians Degrees Radians Exact Approximate Exact Approximate 0 0 0 90 1.57 30 .52 180 3.14 45 .79 270 4.71 60 1.05 360 2 6.28 Equivalent Angles in Degrees and Radians
Find each function value. a) Convert radians to degrees. b) Example: Finding Function Values of Angles in Radian Measure