Finding an upper bound for a contour integral (Complex)

In summary, the problem involves finding an upper bound for the contour integral of e^2z - z^2 over a circular arc and a line segment. The length of the arc and segment are given as pi/6 and 1 respectively. The solution involves using the triangle inequality and converting e^z to its polar form.
  • #1
Zeeree
5
0
C1 1. Homework Statement :
Using the ML inequality, I have to find an upper bound for the contour integral of \int e^2z - z^2 \, dz
where the contour C = C1 + C2.

C1 is the circular arc from point A(sqrt(3)/2, 1/2) to B(1/2, sqrt(3)/2) and C2 is the line segment from the origin to B.


Homework Equations

The Attempt at a Solution



I figured I have to find M1 and M2, and also L1 and L2 given the two different contours. Along C1, I have found the length to be pi/6 by integrating a parameterized equation of the unit circle from pi/6 to pi/3. I have also found the length along C2 to be 1 (no surprises here)

However, I've hit a bump when trying to find the upper bound for e^2z - z^2.
I figured I should use the triangle inequality i.e. |e^2z - z^2|
<= |e^2z| + |-z^2|
= |e^2z| + |z^2|
= |e^2z| + |z|^2
= |e^2z| + 1 (since the length of the line segment is one).

I'm kind of stuck when it comes to the e^2z. It's the same problem for finding the upper bound on C2 as well.

I'm sorry for not using Latex. I tried formatting it but it doesn't come out as intended in the Preview, so I decided not to take the risk of fudging it up and making it look confusing. I'm quite sleepy, sorry.
[/B]
 
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  • #2
If [itex]z = x + iy[/itex] then [itex]e^z = e^x (\cos y + i \sin y)[/itex]...
 
  • #3
pasmith said:
If [itex]z = x + iy[/itex] then [itex]e^z = e^x (\cos y + i \sin y)[/itex]...
Thank you so much, I've got it :)
 

1. What is an upper bound for a contour integral?

An upper bound for a contour integral is the maximum possible value that the integral can take. It is used to determine the range of values that the integral can have, and is often necessary in mathematical calculations and proofs.

2. How is an upper bound for a contour integral calculated?

The calculation of an upper bound for a contour integral depends on the specific function being integrated and the shape of the contour. In general, it involves finding the maximum value of the function along the contour and then multiplying it by the length of the contour.

3. Why is it important to find an upper bound for a contour integral?

Finding an upper bound for a contour integral is important because it helps us determine the accuracy of numerical approximations and estimates. It also allows us to prove the convergence of certain integrals and understand the behavior of complex functions.

4. What is the relationship between the contour and the upper bound for a contour integral?

The contour and the upper bound for a contour integral are closely related, as the shape and size of the contour directly affect the value of the upper bound. A larger and more complex contour will generally have a larger upper bound, while a simpler and smaller contour will have a smaller upper bound.

5. Are there any limitations to finding an upper bound for a contour integral?

Yes, there are limitations to finding an upper bound for a contour integral. The calculation can become increasingly complex for more complicated functions and contours, making it difficult to determine an accurate upper bound. Additionally, certain integrals may not have a finite upper bound, making it impossible to find a single value for the upper bound.

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