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Ch. 1 - Angles and the Trigonometric Functions
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Not the one you use?Change textbook
Chapter 1, Problem 15

The unit circle has been divided into twelve equal arcs, corresponding to t-values of
0, πœ‹/6, πœ‹/3, πœ‹/2, 2πœ‹/3, 5πœ‹/6, πœ‹, 7πœ‹/6, 4πœ‹/3, 3πœ‹/2, 5πœ‹/3, 11πœ‹/6, and 2πœ‹


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.
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sin 3πœ‹/2

Verified step by step guidance
1
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.
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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.
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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.
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Related Practice
Textbook Question

In Exercises 9–16, use the given triangles to evaluate each expression. If necessary, express the value without a square root in the denominator by rationalizing the denominator.

sin πœ‹/4 - cos πœ‹/4

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Textbook Question

In Exercises 13–17, find a positive angle less than 360Β° or 2πœ‹ that is coterminal with the given angle. -445Β°

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Textbook Question
In Exercises 5–18, the unit circle has been divided into twelve equal arcs, corresponding to t-values of0, πœ‹, πœ‹, πœ‹, 2πœ‹, 5πœ‹, πœ‹, 7πœ‹, 4πœ‹, 3πœ‹, 5πœ‹, 11πœ‹, and 2πœ‹.6 3 2 3 6 6 3 2 3 6Use 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.

In Exercises 11–18, continue to refer to the figure at the bottom of the previous page.cos 3πœ‹/2
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Textbook Question

In Exercises 9–16, use the given triangles to evaluate each expression. If necessary, express the value without a square root in the denominator by rationalizing the denominator.

tan πœ‹/4 + csc πœ‹/6

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Textbook Question
In Exercises 5–18, the unit circle has been divided into twelve equal arcs, corresponding to t-values of0, πœ‹, πœ‹, πœ‹, 2πœ‹, 5πœ‹, πœ‹, 7πœ‹, 4πœ‹, 3πœ‹, 5πœ‹, 11πœ‹, and 2πœ‹.6 3 2 3 6 6 3 2 3 6Use 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.

In Exercises 11–18, continue to refer to the figure at the bottom of the previous page.sec 5πœ‹/3
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Textbook Question
In Exercises 5–18, the unit circle has been divided into twelve equal arcs, corresponding to t-values of0, πœ‹, πœ‹, πœ‹, 2πœ‹, 5πœ‹, πœ‹, 7πœ‹, 4πœ‹, 3πœ‹, 5πœ‹, 11πœ‹, and 2πœ‹.6 3 2 3 6 6 3 2 3 6Use 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.

In Exercises 11–18, continue to refer to the figure at the bottom of the previous page.tan 3πœ‹/2
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