Change of variable in a double integral

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Homework Help Overview

The discussion revolves around a double integral involving a change of variables, specifically related to the transformation of coordinates in the context of an ellipse and a resulting circle. Participants are exploring the implications of these transformations on the boundaries of integration.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to determine the boundaries for the variable theta after substituting expressions for x and y into the ellipse equation. They express uncertainty about the range for theta and suggest it might be from zero to pi without justification. Another participant proposes that the range should be from zero to two pi to cover the entire circle.

Discussion Status

The discussion is ongoing, with differing opinions on the appropriate range for theta. Some guidance has been offered regarding the range needed to sweep out the entire circle, but no consensus has been reached.

Contextual Notes

Participants are working under the constraints of a homework problem, which may limit the information available for making definitive conclusions about the boundaries of integration.

rashida564
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Homework Statement
The image bellow is the question
Relevant Equations
Jacobian
Hi everyone, I tried to solve the last part of the question, I substituted back the expression of x and y into the equation of the ellipse, I got that r=1 or r=-1. But got no idea how to find the boundary for theta, I got a guess that, It should be from zero to pi. But got no reason why to believe this.
 

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rashida564 said:
Homework Statement:: The image bellow is the question
Homework Equations:: Jacobian

Hi everyone, I tried to solve the last part of the question, I substituted back the expression of x and y into the equation of the ellipse, I got that r=1 or r=-1. But got no idea how to find the boundary for theta, I got a guess that, It should be from zero to pi. But got no reason why to believe this.
After the transformation, the resulting figure is a circle of radius 1, centered at the origin. If r ranges from 0 to 1, what needs to be the range for ##\theta## to sweep out the whole circle?
 
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Likes   Reactions: vanhees71 and scottdave
From zero to two pi, thanks man
 
Last edited by a moderator:
rashida564 said:
From zero to two pi, thanks man
Right.

BTW, I edited your post. You quoted me as saying "From zero to two pi." I didn't say this, so it's misleading to quote me.
 

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