Table of contents
- 0. Review of College Algebra4h 43m
- 1. Measuring Angles39m
- 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
Defining the Unit Circle
Problem 3.67
Textbook Question
Find the exact value of s in the given interval that has the given circular function value.
[π/2, π] ; sin s = 1/2
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1
Identify the interval [\(\frac{\pi}{2}, \pi\)] which corresponds to the second quadrant of the unit circle.
Recall that in the second quadrant, the sine function is positive.
Recognize that \(\sin s = \frac{1}{2}\) is a common angle value, typically associated with \(s = \frac{\pi}{6}\) or \(s = \frac{5\pi}{6}\).
Since \(\frac{\pi}{6}\) is not in the interval [\(\frac{\pi}{2}, \pi\)], consider the angle \(s = \frac{5\pi}{6}\) which is in the second quadrant.
Verify that \(\sin(\frac{5\pi}{6}) = \frac{1}{2}\) to ensure the solution is correct.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Unit Circle
The unit circle is a circle with a radius of one centered at the origin of a coordinate plane. It is fundamental in trigonometry as it provides a geometric interpretation of the sine, cosine, and tangent functions. The coordinates of points on the unit circle correspond to the cosine and sine values of angles, allowing for the determination of trigonometric function values for various angles.
Recommended video:
Introduction to the Unit Circle
Sine Function
The sine function, denoted as sin(θ), represents the ratio of the length of the opposite side to the hypotenuse in a right triangle. In the context of the unit circle, it gives the y-coordinate of a point on the circle corresponding to an angle θ. Understanding the sine function is crucial for solving equations involving sine values, such as finding angles that yield specific sine outputs.
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Graph of Sine and Cosine Function
Inverse Trigonometric Functions
Inverse trigonometric functions, such as arcsin, are used to find angles when the value of a trigonometric function is known. For example, if sin(s) = 1/2, then s can be determined using arcsin(1/2). It is important to consider the range of the inverse functions and the specified interval when solving for angles, as multiple angles can yield the same sine value.
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Introduction to Inverse Trig Functions
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