Express the following as a function of a positive acute angle: cos 242°

Trigonometry (11th Edition)
11th Edition
ISBN:9780134217437
Author:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Publisher:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Chapter1: Trigonometric Functions
Section: Chapter Questions
Problem 1RE: 1. Give the measures of the complement and the supplement of an angle measuring 35°.
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### Problem:

**Express the following as a function of a positive acute angle:**

\[ \cos 242^\circ \]

### Explanation:

To convert \(\cos 242^\circ \) into the function of a positive acute angle:

1. **Understand the angle location**: 
   - \(242^\circ\) is in the third quadrant since it is between \(180^\circ\) and \(270^\circ\).

2. **Reference angle calculation**:
   - The reference angle for an angle in the third quadrant is determined by subtracting \(180^\circ\) from the given angle:
   \[
   242^\circ - 180^\circ = 62^\circ
   \]

3. **Cosine function properties**:
   - The cosine of an angle in the third quadrant is negative.
   - Therefore, \(\cos 242^\circ\) is equal to the negative of the cosine of its reference angle \(62^\circ\).

4. **Expressing the function**:
   \[
   \cos 242^\circ = -\cos 62^\circ
   \]

So, the final expression is:
\[ \cos 242^\circ = -\cos 62^\circ \]
Transcribed Image Text:### Problem: **Express the following as a function of a positive acute angle:** \[ \cos 242^\circ \] ### Explanation: To convert \(\cos 242^\circ \) into the function of a positive acute angle: 1. **Understand the angle location**: - \(242^\circ\) is in the third quadrant since it is between \(180^\circ\) and \(270^\circ\). 2. **Reference angle calculation**: - The reference angle for an angle in the third quadrant is determined by subtracting \(180^\circ\) from the given angle: \[ 242^\circ - 180^\circ = 62^\circ \] 3. **Cosine function properties**: - The cosine of an angle in the third quadrant is negative. - Therefore, \(\cos 242^\circ\) is equal to the negative of the cosine of its reference angle \(62^\circ\). 4. **Expressing the function**: \[ \cos 242^\circ = -\cos 62^\circ \] So, the final expression is: \[ \cos 242^\circ = -\cos 62^\circ \]
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