Change of variables to evaluate the integral

In summary, the conversation revolved around a homework problem involving transformations and Jacobians. The person asking for help uploaded a picture of the problem and asked for confirmation on their solution. The expert confirmed that the solution was mostly correct, but suggested that the limits of the integrals in the last line may be incorrect.
  • #1
yis
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Homework Statement


these are on the picture

Homework Equations


transformation, jacobian

The Attempt at a Solution


I don't know how to enter the equation, so i uploaded the picture..
is it alright?
I think I solved it somehow, but not quite sure if it is right...
please tell me if there's a wrong process.
thank you..

if you can't see the image, this link would be ok..
http://image.kilho.net/?pk=1599118

e0cad876d79ad2c1247fdf7f5f23cc81d5510088a0ab52a2201560d0464e5d5f41a98be0d63fa48a90a5194b571ad076.jpg
 
Last edited:
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  • #2
The link to the image reports back with "401 Access Denied."
 
  • #3
Looks ok to me (and the link works).
 
  • #4
Looks right except for the limits of the integrals at the very last line that seem wrong.
 
  • #5
I understand the importance of using appropriate change of variables techniques to evaluate integrals in order to simplify complex calculations. In this problem, the transformation and Jacobian methods can be used to change the variables in the given integral and make it easier to solve.

Firstly, we can use the transformation method to change the variables by setting u = x + y and v = x - y. This transformation allows us to rewrite the given integral as an integral over u and v, which can be easier to integrate. However, we must also take into account the change in the limits of integration for u and v.

Next, we can use the Jacobian method to determine the relationship between the original variables (x and y) and the new variables (u and v). This involves calculating the determinant of the Jacobian matrix, which represents the partial derivatives of u and v with respect to x and y. This will help us to properly adjust the limits of integration for the new variables.

By using these techniques, we can simplify the given integral and solve it with ease. However, it is important to carefully check our work and make sure all steps are correct in order to obtain an accurate solution.
 

FAQ: Change of variables to evaluate the integral

What is a change of variables and why is it used in evaluating integrals?

A change of variables is a mathematical technique used to simplify the evaluation of integrals. It involves substituting a new variable for the original variable in the integrand, allowing for a more manageable integration process.

What are the steps involved in using change of variables to evaluate an integral?

The first step is to identify the appropriate substitution, usually by looking for patterns or using trigonometric identities. Next, the limits of integration must be adjusted to match the new variable. Then, the integrand is rewritten in terms of the new variable. Finally, the integral is evaluated and the answer is converted back to the original variable.

What are some common substitutions used in change of variables?

Some common substitutions include u-substitution, trigonometric substitutions, and polynomial substitutions. These substitutions are chosen based on the form of the integrand and the desired outcome.

What are the benefits of using change of variables in evaluating integrals?

Change of variables allows for the simplification and transformation of complicated integrals into more manageable forms. It also helps to solve integrals that would otherwise be difficult or impossible to solve using traditional techniques.

Are there any limitations or precautions to consider when using change of variables?

One limitation is that not all integrals can be solved using change of variables, and some substitutions may not lead to a simpler integral. It is also important to make sure the limits of integration are properly adjusted and to be mindful of any restrictions on the new variable. Additionally, it is important to check the final answer by differentiating to ensure it is correct.

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