For each expression, identify which coterminal angle to use & determine the exact value of the expression.
Table of contents
- 0. Review of College Algebra4h 43m
- 1. Measuring Angles40m
- 2. Trigonometric Functions on Right Triangles2h 5m
- 3. Unit Circle1h 19m
- 4. Graphing Trigonometric Functions1h 19m
- 5. Inverse Trigonometric Functions and Basic Trigonometric Equations1h 41m
- 6. Trigonometric Identities and More Equations2h 34m
- 7. Non-Right Triangles1h 38m
- 8. Vectors2h 25m
- 9. Polar Equations2h 5m
- 10. Parametric Equations1h 6m
- 11. Graphing Complex Numbers1h 7m
3. Unit Circle
Reference Angles
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Identify the reference angle of each given angle.
210°
A
30°
B
45°
C
60°

1
Understand the concept of a reference angle: A reference angle is the smallest angle that the terminal side of a given angle makes with the x-axis. It is always positive and less than or equal to 90°.
For the angle 210°, first determine which quadrant it is in. Since 210° is greater than 180° and less than 270°, it is in the third quadrant.
To find the reference angle for an angle in the third quadrant, subtract 180° from the given angle. So, for 210°, calculate 210° - 180°.
For the angle 45°, since it is already less than 90°, it is in the first quadrant. The reference angle for any angle in the first quadrant is the angle itself, so the reference angle is 45°.
For the angle 60°, it is also in the first quadrant as it is less than 90°. Therefore, the reference angle is the angle itself, which is 60°.
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Multiple Choice
Reference Angles practice set
