In Exercises 87–92, find the exact value of each expression. Write the answer as a single fraction. Do not use a calculator. sin 𝜋/3 cos 𝜋 - cos 𝜋/3 sin 3𝜋/2
Table of contents
- 0. Review of College Algebra4h 45m
- 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
Problem 44
Textbook Question
In Exercises 44–48, find the reference angle for each angle.
265°
Verified step by step guidance1
Identify the quadrant in which the angle 265° lies. Since 265° is between 180° and 270°, it is in the third quadrant.
Recall that the reference angle is the acute angle formed between the terminal side of the given angle and the x-axis.
For angles in the third quadrant, the reference angle \( \theta_r \) is found by subtracting 180° from the given angle: \( \theta_r = \theta - 180^\circ \).
Substitute the given angle into the formula: \( \theta_r = 265^\circ - 180^\circ \).
Simplify the expression to find the reference angle.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Reference Angle
A reference angle is the acute angle formed between the terminal side of a given angle and the x-axis. It is always positive and less than or equal to 90°, used to simplify trigonometric calculations by relating any angle to an angle in the first quadrant.
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Standard Position of an Angle
An angle in standard position has its vertex at the origin and its initial side along the positive x-axis. The angle is measured counterclockwise for positive angles and clockwise for negative angles, which helps determine the quadrant where the terminal side lies.
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Quadrants and Angle Measurement
The coordinate plane is divided into four quadrants, each spanning 90°. Knowing the quadrant of an angle helps find the reference angle by subtracting the angle from the nearest x-axis boundary (0°, 90°, 180°, 270°, or 360°), depending on the quadrant.
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