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Ch. 1 - Angles and the Trigonometric Functions
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Non è quello che usi tu?Cambia libro di testo
Capitolo 1, Problema 20

In Exercises 19–24, a. Use the unit circle shown for Exercises 5–18 to find the value of the trigonometric function. b. Use even and odd properties of trigonometric functions and your answer from part (a) to find the value of the same trigonometric function at the indicated real number. cos 𝜋/3Unit circle with coordinates and angles for trigonometric functions in trigonometry course.

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1
Locate the angle \( \frac{\pi}{3} \) on the unit circle. It corresponds to the point \( \left( \frac{1}{2}, \frac{\sqrt{3}}{2} \right) \).
Identify the cosine value of \( \frac{\pi}{3} \) from the unit circle, which is the x-coordinate of the point, \( \frac{1}{2} \).
Recall the even property of cosine: \( \cos(-x) = \cos(x) \).
Use the even property to find \( \cos(-\frac{\pi}{3}) \), which is also \( \frac{1}{2} \).
Conclude that the cosine value for both \( \frac{\pi}{3} \) and \( -\frac{\pi}{3} \) is \( \frac{1}{2} \).

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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 representation of the sine, cosine, and tangent functions. The coordinates of points on the unit circle correspond to the cosine and sine values of angles measured from the positive x-axis, allowing for easy calculation of trigonometric functions.
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Introduction to the Unit Circle

Trigonometric Functions

Trigonometric functions, such as sine, cosine, and tangent, relate the angles of a triangle to the lengths of its sides. In the context of the unit circle, the cosine of an angle is the x-coordinate, while the sine is the y-coordinate of the corresponding point on the circle. Understanding these functions is crucial for solving problems involving angles and their relationships in various mathematical contexts.
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Introduction to Trigonometric Functions

Even and Odd Properties

Trigonometric functions exhibit specific symmetry properties: cosine is an even function, meaning cos(-x) = cos(x), while sine and tangent are odd functions, meaning sin(-x) = -sin(x) and tan(-x) = -tan(x). These properties allow for simplifications when calculating trigonometric values for negative angles or angles greater than π, making it easier to find values using known angles on the unit circle.
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Even and Odd Identities
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Domanda del libro di testo
In Exercises 17–20, θ is an acute angle and sin θ and cos θ are given. Use identities to find tan θ, csc θ, sec θ, and cot θ. Where necessary, rationalize denominators. sin θ = 3/5, cos θ = 4/5
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In Exercises 19–24, a. Use the unit circle shown for Exercises 5–18 to find the value of the trigonometric function. b. Use even and odd properties of trigonometric functions and your answer from part (a) to find the value of the same trigonometric function at the indicated real number. cos (-𝜋/6)

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In Exercises 21–24, θ is an acute angle and sin θ is given. Use the Pythagorean identity sin²θ + cos²θ = 1 to find cos θ. sin θ = 6/7
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In Exercises 17–20, θ is an acute angle and sin θ and cos θ are given. Use identities to find tan θ, csc θ, sec θ, and cot θ. Where necessary, rationalize denominators. __ sin θ = 6, cos θ = √13 7 7
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Domanda del libro di testo
In Exercises 5–18, the unit circle has been divided into twelve equal arcs, corresponding to t-values of 0, 𝜋, 𝜋, 𝜋, 2𝜋, 5𝜋, 𝜋, 7𝜋, 4𝜋, 3𝜋, 5𝜋, 11𝜋, and 2𝜋. 6 3 2 3 6 6 3 2 3 6 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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Domanda del libro di testo
In Exercises 19–24, a. Use the unit circle shown for Exercises 5–18 to find the value of the trigonometric function. b. Use even and odd properties of trigonometric functions and your answer from part (a) to find the value of the same trigonometric function at the indicated real number. sin 5𝜋/6

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