Evaluate x/10 Than S 11√1+ cos 10x dx. 0

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
Question
### Evaluate the Integral

Given the integral to evaluate:

\[ \int_{0}^{\frac{\pi}{10}} 11 \sqrt{1 + \cos{10x}} \, dx \]

Let's solve this step by step.

### Step-by-Step Solution:

1. **Substitution**:
   Let \( u = 10x \). Then \( du = 10 \, dx \) or \( dx = \frac{du}{10} \).

2. **Change Limits**:
   When \( x = 0 \), \( u = 0 \).
   When \( x = \frac{\pi}{10} \), \( u = \pi \).

3. **Transform the Integral**:
   Substitute the variables and limits:
   
   \[ \int_{0}^{\pi} 11 \sqrt{1 + \cos{u}} \cdot \frac{du}{10} \]
   
   \[ = \frac{11}{10} \int_{0}^{\pi} \sqrt{1 + \cos{u}} \, du \]

4. **Simplify**:
   Use trigonometric identities to simplify \( \sqrt{1 + \cos{u}} \):
   
   \[ 1 + \cos{u} = 2 \cos^2{\left(\frac{u}{2}\right)} \]
   
   Therefore,
   
   \[ \sqrt{1 + \cos{u}} = \sqrt{2} \left| \cos{\left(\frac{u}{2}\right)} \right| \]
   
   Since \( u \) ranges from 0 to \( \pi \), \( \cos{\left(\frac{u}{2}\right)} \) is non-negative. Thus,
   
   \[ \sqrt{1 + \cos{u}} = \sqrt{2} \cos{\left(\frac{u}{2}\right)} \]

5. **Integrate**:
   Substitute back in the integral:
   
   \[ = \frac{11}{10} \int_{0}^{\pi} \sqrt{2} \cos{\left(\frac{u}{2}\right)} \, du \]
   
   \[ = \frac{11 \sqrt{2}}{10} \int_{0}^{\pi} \cos{\left(\frac{u}{2}\right)}
Transcribed Image Text:### Evaluate the Integral Given the integral to evaluate: \[ \int_{0}^{\frac{\pi}{10}} 11 \sqrt{1 + \cos{10x}} \, dx \] Let's solve this step by step. ### Step-by-Step Solution: 1. **Substitution**: Let \( u = 10x \). Then \( du = 10 \, dx \) or \( dx = \frac{du}{10} \). 2. **Change Limits**: When \( x = 0 \), \( u = 0 \). When \( x = \frac{\pi}{10} \), \( u = \pi \). 3. **Transform the Integral**: Substitute the variables and limits: \[ \int_{0}^{\pi} 11 \sqrt{1 + \cos{u}} \cdot \frac{du}{10} \] \[ = \frac{11}{10} \int_{0}^{\pi} \sqrt{1 + \cos{u}} \, du \] 4. **Simplify**: Use trigonometric identities to simplify \( \sqrt{1 + \cos{u}} \): \[ 1 + \cos{u} = 2 \cos^2{\left(\frac{u}{2}\right)} \] Therefore, \[ \sqrt{1 + \cos{u}} = \sqrt{2} \left| \cos{\left(\frac{u}{2}\right)} \right| \] Since \( u \) ranges from 0 to \( \pi \), \( \cos{\left(\frac{u}{2}\right)} \) is non-negative. Thus, \[ \sqrt{1 + \cos{u}} = \sqrt{2} \cos{\left(\frac{u}{2}\right)} \] 5. **Integrate**: Substitute back in the integral: \[ = \frac{11}{10} \int_{0}^{\pi} \sqrt{2} \cos{\left(\frac{u}{2}\right)} \, du \] \[ = \frac{11 \sqrt{2}}{10} \int_{0}^{\pi} \cos{\left(\frac{u}{2}\right)}
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