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
Defining the Unit Circle
Problem 3
Textbook Question
CONCEPT PREVIEW Match each trigonometric function in Column I with its value in Column II. Choices may be used once, more than once, or not at all.

tan 45°
Verified step by step guidance1
Identify the trigonometric function given explicitly: tan 45°. Recall that tan 45° equals 1, so match tan 45° with value B (1).
Recall the common exact values of sine, cosine, and tangent for special angles such as 30°, 45°, and 60°. For example, sin 30° = 1/2, cos 60° = 1/2, sin 45° = cos 45° = √2/2, tan 60° = √3, and so on.
Match each trigonometric function from Column I with its corresponding exact value from Column II by comparing the known values. For instance, if you see sin 30°, match it with C (1/2); if you see cos 45°, match it with H (√2/2).
Use the Pythagorean identities and reciprocal relationships if needed to confirm matches. For example, since tan θ = sin θ / cos θ, if you know sin and cos values, you can find tan values to help with matching.
Double-check that each value from Column II is used appropriately according to the function's known exact values, and ensure no mismatches or contradictions occur.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Basic Trigonometric Ratios
Trigonometric functions such as sine, cosine, and tangent relate the angles of a right triangle to the ratios of its sides. For example, tan 45° equals 1 because the opposite and adjacent sides are equal. Understanding these fundamental ratios is essential for matching functions to their values.
Recommended video:
Introduction to Trigonometric Functions
Special Angles and Their Values
Certain angles like 30°, 45°, and 60° have well-known exact trigonometric values involving square roots and fractions. Memorizing these special angle values, such as sin 30° = ½ or cos 60° = ½, helps quickly identify correct matches without calculation.
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45-45-90 Triangles
Simplification of Radical Expressions
Trigonometric values often involve radicals like √2 or √3, sometimes divided by integers. Being able to simplify and recognize equivalent radical expressions, such as √3/2 or 2√3/3, is crucial for correctly matching the function values given in different forms.
Recommended video:
Simplifying Trig Expressions
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Related Practice
Textbook Question
In Exercises 25–32, the unit circle has been divided into eight equal arcs, corresponding to t-values of0, 𝜋, 𝜋, 3𝜋, 𝜋, 5𝜋, 3𝜋, 7𝜋, and 2𝜋.4 2 4 4 2 4 a. Use the (x,y) coordinates in the figure to find the value of the trigonometric function.b. Use periodic properties and your answer from part (a) to find the value of the same trigonometric function at the indicated real number.tan 𝜋
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