Help With Integral Problem - Double Integration?

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In summary, the conversation is about a person seeking help with an integral problem and others offering suggestions and guidance. The original poster had written down the problem incorrectly but later corrected it and thanked the others for their help. They discussed the use of the "douple integration" method and the possibility of using the imaginary error function. They also shared a website that could assist with finding the solution and discussed trying to figure out the solution by hand. One person suggested cheating by calculating the derivative of the result and writing the calculation in reverse order, while another suggested looking at the Mathematica package for guidance.
  • #1
Ami
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Homework Statement



http://www4.0zz0.com/2007/02/16/20/74624071.bmp


Homework Equations


Can anybody help me with this integral problem?Please.


The Attempt at a Solution



Is the only solution by the "douple integration" method ?
 
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  • #2
What have you tried?
 
  • #3
Calc I or Calc II? Are you sure you wrote that problem down correctly?

(edit: have you heard of the imaginary error function? Either that, or I'm completely blanking out on this one.)
 
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  • #4
I'm really sorry. I've written the problem down uncorrectly:confused:

This is the right one:_
http://www4.0zz0.com/2007/02/16/21/95988123.bmp

sorry.And thanks for your replies.
 
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  • #5
Try rewriting the problem;

[tex]\int e^{-x^2}\cdot e^{-\frac{1}{x^2}} dx[/tex]
 
  • #6
I tried this step,but I couldn't continue.

Thanks for your reply "Hootenanny"
 
  • #7
Maybe we need "douple integration" here.
 
  • #8
cheat with this site:


http://integrals.wolfram.com/index.jsp


enter your function as follows: Exp[-x^2-1/x^2]

You will see that it is not an easy one.

However, I guess that for a definite integral {-Inf,+Inf} it could be easier.
Are you sure you want the indefinite integral?

If yes, you can still try to figure out out to get by hand the result mathematica will show you.

The result is:

Integrate[Exp[-x^2 - 1/x^2], x] ==
(Sqrt[Pi]*((1 + Erf[-x^(-1) + x])/E^2 + E^2*(-1 + Erf[x^(-1) + x])))/4
 
  • #9
Thank you very much for the wonderful site,and for replying.

I've tried it,and I saw the result. But as you said,I want to figure out how to get by hand the result.

I still need help.
 
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  • #10
I want to figure out how to get by hand the result

That's where cheating becomes really an art.
Try calculating the derivate of the result and write the calculation in reverse order.

In this process you may have some good idea.

Another method is to look in the Mathematica package how it does that.
It is very difficult to read, but it is easy to guess the ingredients.
Probably a standard form we be used and some integral table results (not many since erf is an easy function).
But you need Mathematica ... and that's very expensive
 
  • #11
Great ideas,especially that one about cheating:smile: :wink:

I will try this one,because I can't use Mathematica package right now.
And we will see:rolleyes:

Thanks for your great help.
 

FAQ: Help With Integral Problem - Double Integration?

What is double integration and why is it important?

Double integration is a mathematical technique used to find the area under a two-dimensional curve or surface. It is important in many fields of science, including physics, engineering, and economics, as it allows for the calculation of quantities such as volume, mass, and work.

How do I solve a double integration problem?

To solve a double integration problem, you will need to first identify the limits of integration, which define the boundaries of the region you are integrating over. Then, you will need to set up the integral using the appropriate formula, and evaluate it using either analytical or numerical methods.

What are some common challenges when working with double integrals?

One common challenge when working with double integrals is correctly identifying the limits of integration, as they can be difficult to visualize in some cases. Another challenge can be determining the appropriate formula to use for the given problem, as there are different types of double integrals depending on the type of region being integrated over.

How can I check my solution to a double integration problem?

You can check your solution to a double integration problem by using a graphing calculator or computer software to graph the region being integrated over and compare it to your calculated answer. Additionally, you can check for errors by taking the partial derivatives of your solution and ensuring they match the original function.

What are some real-world applications of double integration?

Double integration has many real-world applications, including calculating the center of mass of an object, determining the moment of inertia of a rigid body, and finding the total charge or mass of a two-dimensional object. It is also used in economics to calculate consumer surplus and producer surplus in supply and demand models.

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