Find the domain of y = cos ¹(2x).

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 37:**

Find the domain of \( y = \cos^{-1}(2x) \).

**Solution:**

The function \( y = \cos^{-1}(x) \) is defined for \( x \) in the interval \([-1, 1]\). Therefore, for the given function \( y = \cos^{-1}(2x) \), the expression inside the inverse cosine, \( 2x \), must also be within the interval \([-1, 1]\).

**Steps to find the domain:**

1. **Set the expression within the valid range:**

   \[
   -1 \leq 2x \leq 1
   \]

2. **Solve the inequalities:**

   - Divide each part of the inequality by 2:
     \[
     -\frac{1}{2} \leq x \leq \frac{1}{2}
     \]

Thus, the domain of \( y = \cos^{-1}(2x) \) is:

\[
x \in \left[-\frac{1}{2}, \frac{1}{2}\right]
\]

This means that the function is defined for all \( x \) within this interval.
Transcribed Image Text:**Problem 37:** Find the domain of \( y = \cos^{-1}(2x) \). **Solution:** The function \( y = \cos^{-1}(x) \) is defined for \( x \) in the interval \([-1, 1]\). Therefore, for the given function \( y = \cos^{-1}(2x) \), the expression inside the inverse cosine, \( 2x \), must also be within the interval \([-1, 1]\). **Steps to find the domain:** 1. **Set the expression within the valid range:** \[ -1 \leq 2x \leq 1 \] 2. **Solve the inequalities:** - Divide each part of the inequality by 2: \[ -\frac{1}{2} \leq x \leq \frac{1}{2} \] Thus, the domain of \( y = \cos^{-1}(2x) \) is: \[ x \in \left[-\frac{1}{2}, \frac{1}{2}\right] \] This means that the function is defined for all \( x \) within this interval.
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