Computing Integrals with Complex Analysis: A Step-by-Step Guide

In summary, complex variables are numbers with both real and imaginary components that are important in mathematics for representing and analyzing functions. Complex integrals differ from real integrals because they can be evaluated along any curve in the complex plane. The process of calculating a complex integral involves breaking it into smaller parts and using techniques such as Cauchy's theorem. The Cauchy-Riemann equations are important in complex analysis for determining if a function is differentiable. Complex integration can also be applied to real-world problems in fields such as physics, engineering, and finance.
  • #1
babyrudin
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Homework Equations



Using complex analysis, compute
[tex]\int_{-\infty}^{\infty} \frac{e^{itx}}{1+x^2}dx [/tex]
where t is real.

The Attempt at a Solution



I'm not good at complex analysis at all and am totally lost. I do know some Fourier analysis though and using it I got
[tex]\pi e^{-|t|}[/tex].
How should I solve it using complex analysis?
 
Last edited:
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  • #2
Try using the Residue Theorem.
 
  • #3
Great, I think I know how to do it now. I was trying the Cauchy integral formula too much. Thanks!
 

1. What are complex variables and why are they important in mathematics?

Complex variables are numbers that contain both a real and an imaginary component. They are important in mathematics because they allow for the representation and analysis of functions that are not possible with real variables. They also have many applications in physics, engineering, and other fields.

2. What is a complex integral and how is it different from a real integral?

A complex integral is the process of calculating the area under a curve in the complex plane. It is different from a real integral because the path of integration can be any curve in the complex plane, rather than just a straight line in the real plane. This allows for more complex and interesting integrals to be evaluated.

3. How do you calculate a complex integral?

The process of calculating a complex integral involves breaking down the integral into smaller parts and using the fundamental theorem of calculus to evaluate each part. The path of integration can also be transformed into a simpler form using techniques such as Cauchy's integral theorem or contour integration.

4. What is the significance of the Cauchy-Riemann equations in complex analysis?

The Cauchy-Riemann equations are a set of conditions that must be satisfied for a complex function to be differentiable. They are important in complex analysis because they provide a way to determine if a function is analytic and can be used to find the derivatives of complex functions.

5. Can complex integration be applied to real-world problems?

Yes, complex integration can be applied to real-world problems in fields such as physics, engineering, and finance. For example, in fluid dynamics, the path of a moving fluid can be represented by a complex function and its integral can be used to calculate properties such as velocity and pressure. In finance, complex integration can be used to model the behavior of stock prices over time.

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