m,neIN ce2 (MTIX) Cos(NTTY) dxdy

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...
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I don't understand how to evaluate this double integral. Can you please explain it to me? Thank you 

### Handwritten Mathematical Derivation

This image presents a mathematical derivation with the following details:

1. **Expression for \( A_{0n} \):**
   - Given conditions: \( n \in \mathbb{N} \)
   - Formula: 
     \[
     A_{0n} = \frac{(-1)^n - 1}{n^2 \pi^2}
     \]

2. **Expression for \( A_{mn} \):**
   - Condition: \( m, n \in \mathbb{N} \)
   - Double integral expression:
     \[
     \iint_{0}^{1} xy \cos(m\pi x) \cos(n\pi y) \, dx \, dy
     \]
   - Simplification using constants:
     \[
     = A_{mn} \cdot \frac{1}{2} \cdot \frac{1}{2}
     \]
   - Further simplification leads to:
     \[
     A_{mn} = 4 \iint_{0}^{1} xy \cos(m\pi x) \cos(n\pi y) \, dx \, dy
     \]
   - Evaluating the integral yields:
     \[
     = 4 \left( \frac{(-1)^m - 1}{m^2 \pi^2} \right) \left( \frac{(-1)^n - 1}{n^2 \pi^2} \right)
     \]

### Explanation:
- The derivation involves calculating specific coefficients \( A_{0n} \) and \( A_{mn} \) which arise in contexts such as Fourier series or similar mathematical constructs.
- The integrals represent a form of orthogonality and simplification involving trigonometric functions, often used in solving PDEs.
- The expression involves cosine functions, indicating that the original problem might relate to periodic signals or boundary value problems.

This presentation allows students to understand the transition from the integral form to a simplified algebraic expression by evaluating definite integrals involving trigonometric functions.
Transcribed Image Text:### Handwritten Mathematical Derivation This image presents a mathematical derivation with the following details: 1. **Expression for \( A_{0n} \):** - Given conditions: \( n \in \mathbb{N} \) - Formula: \[ A_{0n} = \frac{(-1)^n - 1}{n^2 \pi^2} \] 2. **Expression for \( A_{mn} \):** - Condition: \( m, n \in \mathbb{N} \) - Double integral expression: \[ \iint_{0}^{1} xy \cos(m\pi x) \cos(n\pi y) \, dx \, dy \] - Simplification using constants: \[ = A_{mn} \cdot \frac{1}{2} \cdot \frac{1}{2} \] - Further simplification leads to: \[ A_{mn} = 4 \iint_{0}^{1} xy \cos(m\pi x) \cos(n\pi y) \, dx \, dy \] - Evaluating the integral yields: \[ = 4 \left( \frac{(-1)^m - 1}{m^2 \pi^2} \right) \left( \frac{(-1)^n - 1}{n^2 \pi^2} \right) \] ### Explanation: - The derivation involves calculating specific coefficients \( A_{0n} \) and \( A_{mn} \) which arise in contexts such as Fourier series or similar mathematical constructs. - The integrals represent a form of orthogonality and simplification involving trigonometric functions, often used in solving PDEs. - The expression involves cosine functions, indicating that the original problem might relate to periodic signals or boundary value problems. This presentation allows students to understand the transition from the integral form to a simplified algebraic expression by evaluating definite integrals involving trigonometric functions.
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