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Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
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Integrate the following function along the contour C. 

 

## Complex Analysis Integral

### Problem Statement:

Evaluate the following contour integral:

\[ \int_{C} \frac{\sin z}{z^2 - 2iz} \, dz, \]

where the contour \( C \) consists of:
- \( |z| = 3 \) (counterclockwise)
- \( |z| = 1 \) (clockwise)

### Explanation:

This integral problem involves evaluating a complex integral along a given contour consisting of two circles:
1. A counterclockwise path around the circle \(|z| = 3\)
2. A clockwise path around the circle \(|z| = 1\)

The integrand function is \(\frac{\sin z}{z^2 - 2iz}\).

### Analysis:

1. **Singularities**: Determine the singularities of the function \(\frac{\sin z}{z^2 - 2iz}\).
2. **Residue Theorem**: Apply the residue theorem to evaluate the integral around each path.

Analyzing the singularities, we start with the denominator \(z^2 - 2iz\). Factoring it, we have:
\[ z^2 - 2iz = z(z - 2i). \]
So, the singularities \(z = 0\) and \(z = 2i\).

### Steps to Evaluate:

1. **Identify Residues**: Compute the residues of the integrand at the singularities within each contour.
2. **Counterclockwise Contour (|z| = 3)**:
   - Lies outside the singularities \(0\) and \(2i\).
3. **Clockwise Contour (|z| = 1)**:
   - Lies within the singularity \(z = 0\).
   
Use this gathered information to conclude the result of the integral using the residue theorem.

###### Note:

When dealing with such problems, make sure to consider the orientation (clockwise vs counterclockwise) as it affects the sign of the integral.
Transcribed Image Text:## Complex Analysis Integral ### Problem Statement: Evaluate the following contour integral: \[ \int_{C} \frac{\sin z}{z^2 - 2iz} \, dz, \] where the contour \( C \) consists of: - \( |z| = 3 \) (counterclockwise) - \( |z| = 1 \) (clockwise) ### Explanation: This integral problem involves evaluating a complex integral along a given contour consisting of two circles: 1. A counterclockwise path around the circle \(|z| = 3\) 2. A clockwise path around the circle \(|z| = 1\) The integrand function is \(\frac{\sin z}{z^2 - 2iz}\). ### Analysis: 1. **Singularities**: Determine the singularities of the function \(\frac{\sin z}{z^2 - 2iz}\). 2. **Residue Theorem**: Apply the residue theorem to evaluate the integral around each path. Analyzing the singularities, we start with the denominator \(z^2 - 2iz\). Factoring it, we have: \[ z^2 - 2iz = z(z - 2i). \] So, the singularities \(z = 0\) and \(z = 2i\). ### Steps to Evaluate: 1. **Identify Residues**: Compute the residues of the integrand at the singularities within each contour. 2. **Counterclockwise Contour (|z| = 3)**: - Lies outside the singularities \(0\) and \(2i\). 3. **Clockwise Contour (|z| = 1)**: - Lies within the singularity \(z = 0\). Use this gathered information to conclude the result of the integral using the residue theorem. ###### Note: When dealing with such problems, make sure to consider the orientation (clockwise vs counterclockwise) as it affects the sign of the integral.
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