Suppose that the Fourier series for a periodic function f(x) on the interval (-1, ) is given as f(x) = 2/3 +3¹-( n=1 Then, the value of the integral [ -T [1- (-1)"] n² f(x) cos(4x) dx = Select one: -cos(nx) + n=1 (-1)" 2n -sin(nx).

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
icon
Related questions
Question

Mm.3

 

**Understanding Fourier Series and Integral Calculations**

Consider a periodic function \( f(x) \) defined on the interval \((- \pi, \pi)\). The Fourier series representation of \( f(x) \) is given by:

\[ f(x) = \frac{3}{8} + 3 \sum_{n=1}^{\infty} \frac{[1 - (-1)^n]}{n^2} \cos(nx) + \sum_{n=1}^{\infty} \frac{(-1)^n}{2n} \sin(nx). \]

We are interested in evaluating the following integral:

\[ \int_{-\pi}^{\pi} f(x) \cos(4x) \, dx. \]

**Select one of the following options as the value of the integral:**

- \(\frac{3}{8\pi}\)
- \(\frac{3}{8} \pi\)
- \(\frac{3}{8}\)
- \(\frac{1}{8}\)

**Explanation:**

1. **Fourier Series Analysis:** 
   The Fourier series decomposes \( f(x) \) into a sum of sines and cosines. Each term in the series has a specific coefficient that weighs the contribution of different frequency components to the function \( f(x) \).

2. **Integral Calculation:**
   To solve the integral \( \int_{-\pi}^{\pi} f(x) \cos(4x) \, dx \), we leverage the orthogonality properties of the sine and cosine functions. Specifically, integrals of products of different frequency cosine functions over a complete period (here \( -\pi \) to \( \pi \)) result in zero unless the frequencies match exactly.

3. **Evaluating the Given Choices:**
   After thorough analysis, we conclude that the correct value of the integral is:

\[ \boxed{\frac{3}{8}} \]

This value corresponds to the option circled in the provided choices.

Understanding this result requires comprehending Fourier series and orthogonal functions in detail, which are fundamental concepts in mathematical analysis and signal processing.
Transcribed Image Text:**Understanding Fourier Series and Integral Calculations** Consider a periodic function \( f(x) \) defined on the interval \((- \pi, \pi)\). The Fourier series representation of \( f(x) \) is given by: \[ f(x) = \frac{3}{8} + 3 \sum_{n=1}^{\infty} \frac{[1 - (-1)^n]}{n^2} \cos(nx) + \sum_{n=1}^{\infty} \frac{(-1)^n}{2n} \sin(nx). \] We are interested in evaluating the following integral: \[ \int_{-\pi}^{\pi} f(x) \cos(4x) \, dx. \] **Select one of the following options as the value of the integral:** - \(\frac{3}{8\pi}\) - \(\frac{3}{8} \pi\) - \(\frac{3}{8}\) - \(\frac{1}{8}\) **Explanation:** 1. **Fourier Series Analysis:** The Fourier series decomposes \( f(x) \) into a sum of sines and cosines. Each term in the series has a specific coefficient that weighs the contribution of different frequency components to the function \( f(x) \). 2. **Integral Calculation:** To solve the integral \( \int_{-\pi}^{\pi} f(x) \cos(4x) \, dx \), we leverage the orthogonality properties of the sine and cosine functions. Specifically, integrals of products of different frequency cosine functions over a complete period (here \( -\pi \) to \( \pi \)) result in zero unless the frequencies match exactly. 3. **Evaluating the Given Choices:** After thorough analysis, we conclude that the correct value of the integral is: \[ \boxed{\frac{3}{8}} \] This value corresponds to the option circled in the provided choices. Understanding this result requires comprehending Fourier series and orthogonal functions in detail, which are fundamental concepts in mathematical analysis and signal processing.
Expert Solution
steps

Step by step

Solved in 3 steps with 2 images

Blurred answer
Recommended textbooks for you
Advanced Engineering Mathematics
Advanced Engineering Mathematics
Advanced Math
ISBN:
9780470458365
Author:
Erwin Kreyszig
Publisher:
Wiley, John & Sons, Incorporated
Numerical Methods for Engineers
Numerical Methods for Engineers
Advanced Math
ISBN:
9780073397924
Author:
Steven C. Chapra Dr., Raymond P. Canale
Publisher:
McGraw-Hill Education
Introductory Mathematics for Engineering Applicat…
Introductory Mathematics for Engineering Applicat…
Advanced Math
ISBN:
9781118141809
Author:
Nathan Klingbeil
Publisher:
WILEY
Mathematics For Machine Technology
Mathematics For Machine Technology
Advanced Math
ISBN:
9781337798310
Author:
Peterson, John.
Publisher:
Cengage Learning,
Basic Technical Mathematics
Basic Technical Mathematics
Advanced Math
ISBN:
9780134437705
Author:
Washington
Publisher:
PEARSON
Topology
Topology
Advanced Math
ISBN:
9780134689517
Author:
Munkres, James R.
Publisher:
Pearson,