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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 39

In Exercises 35–60, find the reference angle for each angle.
355°

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1
Identify the quadrant in which the angle 355° lies. Since 355° is between 270° and 360°, it is in the fourth quadrant.
Recall that the reference angle is the acute angle formed between the terminal side of the given angle and the x-axis.
For angles in the fourth quadrant, the reference angle \( \theta_{ref} \) is calculated by subtracting the angle from 360°: \( \theta_{ref} = 360^\circ - \theta \).
Substitute the given angle into the formula: \( \theta_{ref} = 360^\circ - 355^\circ \).
Simplify the expression to find the reference angle.

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Key Concepts

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

Reference Angle

A reference angle is the acute angle formed between the terminal side of a given angle and the x-axis. It is always positive and less than or equal to 90°, used to simplify trigonometric calculations by relating any angle to an acute angle.
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Standard Position of an Angle

An angle in standard position has its vertex at the origin and its initial side along the positive x-axis. The terminal side rotates counterclockwise for positive angles and clockwise for negative angles, determining the angle's quadrant and reference angle.
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Quadrants and Angle Measurement

The coordinate plane is divided into four quadrants, each spanning 90°. Knowing the quadrant of an angle helps find its reference angle by subtracting or adding the angle to the nearest x-axis boundary (0°, 90°, 180°, 270°, or 360°).
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