Math Problem Statement

Compute the following contour integral: I = ∫_C (exp(1/z) / (3z - 4)^2) dz, where the contour C is the unit circle centered on z = 2. State any general results used.

Solution

The problem is asking to compute the contour integral

I=Ce1/z(3z4)2dz,I = \int_C \frac{e^{1/z}}{(3z - 4)^2} \, dz,

where CC is the unit circle centered on z=2z = 2. Let's proceed with solving it step-by-step:


1. Residue Theorem:

The Residue Theorem states that for a closed contour CC and a meromorphic function f(z)f(z), the contour integral is:

Cf(z)dz=2πiRes(f(z),z0),\int_C f(z) \, dz = 2\pi i \cdot \text{Res}(f(z), z_0),

where z0z_0 is the singularity inside CC.


2. Analyzing the Given Integral:

Function to Integrate:

f(z)=e1/z(3z4)2.f(z) = \frac{e^{1/z}}{(3z - 4)^2}.

  • Singularity Analysis: The term (3z4)2(3z - 4)^2 introduces a pole at z=43z = \frac{4}{3} (a double pole).
    The contour CC is a unit circle centered at z=2z = 2. Since z=43z = \frac{4}{3} is outside this circle, no singularities lie inside CC.

3. Conclusion:

If there are no singularities inside the contour CC, the function f(z)f(z) is analytic inside CC, and therefore, by Cauchy's Integral Theorem:

I=Cf(z)dz=0.I = \int_C f(z) \, dz = 0.


Final Answer:

I=0.I = 0.

If you have additional questions or would like me to elaborate on any step, feel free to ask!


Follow-Up Questions:

  1. What is the significance of the Residue Theorem in contour integration?
  2. How does the order of a pole (simple, double, etc.) affect residue computation?
  3. Why is z=43z = \frac{4}{3} not inside the unit circle centered at z=2z = 2?
  4. Can the integral be nonzero if the singularity lies exactly on the contour CC?
  5. How would the answer change if the contour CC were a circle centered at the origin?

Tip:

Always sketch the contour and the location of singularities in the complex plane to verify whether the singularities are inside, outside, or on the contour.

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Math Problem Analysis

Mathematical Concepts

Complex Analysis
Contour Integration
Residue Theorem
Cauchy's Integral Theorem

Formulas

Residue Theorem: ∫_C f(z) dz = 2πi ⋅ Res(f(z), z0)
Cauchy's Integral Theorem: If f(z) is analytic inside and on a simple closed contour C, then ∫_C f(z) dz = 0

Theorems

Residue Theorem
Cauchy's Integral Theorem

Suitable Grade Level

Undergraduate Level (Complex Analysis)