Math Problem Statement

Using Cauchy integral formula, find the value of ∫_C (e^z / (z - π)) dz where C is the circle |z - 1| = 4.

Solution

To solve the given problem using Cauchy's Integral Formula, let's analyze the problem step by step.

The integral is:

Cezzπdz\int_C \frac{e^z}{z - \pi} \, dz

where CC is the circle z1=4|z - 1| = 4.

Step 1: Identify the Function and Pole

The integrand is:

f(z)=ezzπf(z) = \frac{e^z}{z - \pi}

Here, the function f(z)f(z) has a singularity at z=πz = \pi. Since CC is the circle of radius 4 centered at z=1z = 1, the distance from the center of the circle to z=πz = \pi is:

zπ=π1=3.141=2.14|z - \pi| = |\pi - 1| = 3.14 - 1 = 2.14

Since 2.14<42.14 < 4, the singularity z=πz = \pi lies inside the circle.

Step 2: Apply Cauchy's Integral Formula

Cauchy's Integral Formula states that for a function f(z)f(z):

Cf(z)zadz=2πif(a)\int_C \frac{f(z)}{z - a} \, dz = 2\pi i f(a)

Here:

  • f(z)=ezf(z) = e^z
  • a=πa = \pi

So, f(a)=eπf(a) = e^{\pi}.

Step 3: Substitute into the Formula

Using the formula:

Cezzπdz=2πieπ\int_C \frac{e^z}{z - \pi} \, dz = 2\pi i \cdot e^{\pi}

Final Answer:

Cezzπdz=2πieπ\int_C \frac{e^z}{z - \pi} \, dz = 2\pi i e^{\pi}

Let me know if you would like a more detailed explanation or further clarification!


Here are 5 related questions for better understanding:

  1. How does Cauchy's Integral Formula simplify computations of contour integrals?
  2. What happens if the singularity lies outside the contour CC?
  3. Can this integral be solved without using Cauchy's Integral Formula? How?
  4. How would the result change if CC was a different contour not enclosing z=πz = \pi?
  5. What are the geometric implications of the circle z1=4|z - 1| = 4 in the complex plane?

Tip: Always check whether the singularity is inside or outside the contour before applying Cauchy's Integral Formula!

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Math Problem Analysis

Mathematical Concepts

Complex Analysis
Cauchy's Integral Formula
Contour Integration

Formulas

Cauchy's Integral Formula: ∫_C (f(z)/(z - a)) dz = 2πi f(a)

Theorems

Cauchy's Integral Formula

Suitable Grade Level

Undergraduate Mathematics