Concept Check Work each problem. What angle does the line y = β3x make with the positive x-axis?
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
Common Values of Sine, Cosine, & Tangent
Problem 15
Textbook Question
The unit circle has been divided into twelve equal arcs, corresponding to t-values of
0, π/6, π/3, π/2, 2π/3, 5π/6, π, 7π/6, 4π/3, 3π/2, 5π/3, 11π/6, and 2π
Use the (x,y) coordinates in the figure to find the value of each trigonometric function at the indicated real number, t, or state that the expression is undefined.
<IMAGE>
sin 3π/2
Verified step by step guidance1
Recall that on the unit circle, the coordinates of a point corresponding to an angle \(t\) are given by \((\cos t, \sin t)\).
Identify the angle \(t = 3\pi/2\) on the unit circle. This angle corresponds to rotating \(270^\circ\) counterclockwise from the positive x-axis.
Find the coordinates of the point on the unit circle at \(t = 3\pi/2\). This point lies on the negative y-axis.
Since the sine of an angle is the y-coordinate of the corresponding point on the unit circle, write \(\sin 3\pi/2\) as the y-coordinate of that point.
State the value of \(\sin 3\pi/2\) based on the coordinates found, or note if it is undefined (which it is not in this case).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Unit Circle and Radian Measure
The unit circle is a circle with radius 1 centered at the origin of the coordinate plane. Angles on the unit circle are measured in radians, where 2Ο radians correspond to a full rotation of 360Β°. Dividing the circle into twelve equal arcs means each arc measures Ο/6 radians, providing standard angle measures for evaluating trigonometric functions.
Recommended video:
Introduction to the Unit Circle
Coordinates on the Unit Circle and Trigonometric Functions
Each point on the unit circle corresponds to an angle t and has coordinates (x, y), where x = cos(t) and y = sin(t). These coordinates allow direct evaluation of sine and cosine values for given angles. For example, sin(3Ο/2) corresponds to the y-coordinate of the point at angle 3Ο/2.
Recommended video:
Sine, Cosine, & Tangent on the Unit Circle
Definition and Domain of Trigonometric Functions
Sine and cosine functions are defined for all real numbers and correspond to y and x coordinates on the unit circle, respectively. Other functions like tangent are defined as sin(t)/cos(t) and may be undefined where cosine is zero. Understanding when functions are defined or undefined is crucial for correctly evaluating expressions at specific angles.
Recommended video:
Finding the Domain of an Equation
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