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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 1.1.64

In Exercises 57–70, find a positive angle less than or that is coterminal with the given angle. 17πœ‹ /5

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1
Understand that two angles are coterminal if they differ by an integer multiple of \(2\pi\). This means we can add or subtract \(2\pi\) to the given angle to find coterminal angles.
Given the angle \(\frac{17\pi}{5}\), we want to find a positive angle \(\theta\) such that \(0 \leq \theta < 2\pi\) and \(\theta\) is coterminal with \(\frac{17\pi}{5}\).
To do this, subtract multiples of \(2\pi\) from \(\frac{17\pi}{5}\) until the result lies between \(0\) and \(2\pi\). Express \(2\pi\) with denominator 5 as \(\frac{10\pi}{5}\) for easier subtraction.
Calculate \(\frac{17\pi}{5} - 2\pi = \frac{17\pi}{5} - \frac{10\pi}{5} = \frac{7\pi}{5}\). Since \(\frac{7\pi}{5}\) is positive and less than \(2\pi\), this is the coterminal angle you are looking for.
Verify that \(0 \leq \frac{7\pi}{5} < 2\pi\) to confirm the angle is within the desired range.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Coterminal Angles

Coterminal angles are angles that share the same initial and terminal sides but differ by full rotations of 2Ο€ radians. To find a coterminal angle, you add or subtract multiples of 2Ο€ until the angle lies within the desired range, such as between 0 and 2Ο€.
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Angle Measurement in Radians

Angles can be measured in radians, where 2Ο€ radians equal one full rotation (360 degrees). Understanding how to convert and manipulate angles in radians is essential for solving problems involving coterminal angles and angle normalization.
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Finding Positive Angles Less Than or Equal to 2Ο€

To find a positive angle less than or equal to 2Ο€ that is coterminal with a given angle, subtract multiples of 2Ο€ from the angle until the result is within the interval [0, 2Ο€]. This process ensures the angle is expressed in its principal value range.
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