Find all solutions of the equation in the interval [0,2). 1 2 cos 3x =

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 Statement:**

Find all solutions of the equation in the interval \([0, 2\pi)\).

\[
\cos 3x = -\frac{1}{2}
\]

**Solution Explanation:**

To solve this equation, recognize that \(\cos \theta = -\frac{1}{2}\) has solutions where the cosine function takes specific angles. The principal values where cosine equals \(-\frac{1}{2}\) are \( \theta = \frac{2\pi}{3} \) and \(\theta = \frac{4\pi}{3}\) within the interval \([0, 2\pi)\).

Given \(\cos 3x = -\frac{1}{2}\), this implies:

1. \(3x = \frac{2\pi}{3} + 2k\pi\)
2. \(3x = \frac{4\pi}{3} + 2k\pi\)

For each of these general solutions, solve for \(x\):

- From \(3x = \frac{2\pi}{3} + 2k\pi\), divide by 3:

  \[
  x = \frac{2\pi}{9} + \frac{2k\pi}{3}
  \]

- From \(3x = \frac{4\pi}{3} + 2k\pi\), divide by 3:

  \[
  x = \frac{4\pi}{9} + \frac{2k\pi}{3}
  \]

Find values of \(x\) that fall within the interval \([0, 2\pi)\):

1. For \(x = \frac{2\pi}{9} + \frac{2k\pi}{3}\):
   - \(k = 0\): \(x = \frac{2\pi}{9}\)
   - \(k = 1\): \(x = \frac{2\pi}{9} + \frac{2\pi}{3} = \frac{8\pi}{9}\)
   - \(k = 2\): \(x = \frac{2\pi}{9} + \frac{4\pi}{3} = \frac{14\pi}{9}\)
   - \(k = 3\): \(x = \
Transcribed Image Text:**Problem Statement:** Find all solutions of the equation in the interval \([0, 2\pi)\). \[ \cos 3x = -\frac{1}{2} \] **Solution Explanation:** To solve this equation, recognize that \(\cos \theta = -\frac{1}{2}\) has solutions where the cosine function takes specific angles. The principal values where cosine equals \(-\frac{1}{2}\) are \( \theta = \frac{2\pi}{3} \) and \(\theta = \frac{4\pi}{3}\) within the interval \([0, 2\pi)\). Given \(\cos 3x = -\frac{1}{2}\), this implies: 1. \(3x = \frac{2\pi}{3} + 2k\pi\) 2. \(3x = \frac{4\pi}{3} + 2k\pi\) For each of these general solutions, solve for \(x\): - From \(3x = \frac{2\pi}{3} + 2k\pi\), divide by 3: \[ x = \frac{2\pi}{9} + \frac{2k\pi}{3} \] - From \(3x = \frac{4\pi}{3} + 2k\pi\), divide by 3: \[ x = \frac{4\pi}{9} + \frac{2k\pi}{3} \] Find values of \(x\) that fall within the interval \([0, 2\pi)\): 1. For \(x = \frac{2\pi}{9} + \frac{2k\pi}{3}\): - \(k = 0\): \(x = \frac{2\pi}{9}\) - \(k = 1\): \(x = \frac{2\pi}{9} + \frac{2\pi}{3} = \frac{8\pi}{9}\) - \(k = 2\): \(x = \frac{2\pi}{9} + \frac{4\pi}{3} = \frac{14\pi}{9}\) - \(k = 3\): \(x = \
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