Area Calculation for Circle and Cardioid Using Double Integrals

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Homework Help Overview

The discussion revolves around calculating the area between a circle defined by r=1 and a cardioid defined by r=1+cos(θ) using double integrals. Participants express confusion regarding the setup and interpretation of the problem.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the limits for θ and r, with some attempting to visualize the regions involved. Questions arise about the intersection points and the symmetry of the regions.

Discussion Status

The discussion is ongoing, with participants sharing their attempts to visualize the problem and clarify the setup. Some guidance on considering symmetry and the regions of integration has been suggested, but no consensus has been reached.

Contextual Notes

Participants note ambiguity in the problem's wording and the need for a clear understanding of the regions defined by the circle and cardioid. There are references to missing information in visual representations.

stolencookie

Homework Statement


r=1 and r=1+cos(theta), use a double integral to find the area inside the circle r=1 and outside the cardioid r=1+cos(theta)

Homework Equations

The Attempt at a Solution


I am confused on the wording and how to set it up. I tried setting it up by setting theta 0 to pi. and r as 1 to 1+cos(theta). I used r drd(theta) as the equation to use.
 
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stolencookie said:

Homework Statement


r=1 and r=1+cos(theta), use a double integral to find the area inside the circle r=1 and outside the cardioid r=1+cos(theta)
...

I am confused on the wording and how to set it up.
Make a picture !
upload_2017-12-1_18-21-19.png
 

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BvU said:
Make a picture !
View attachment 215925
I did make a picture I am confused by the little piece of the cardoid that isn't in the first quadrant.
 
stolencookie said:
I did make a picture I am confused by the little piece of the cardoid that isn't in the first quadrant.

In the whole plane, what is the region outside the cardioid? What is the region inside the circle? What is the intersection of those two regions?
 
Last edited:
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stolencookie said:
I tried setting it up by setting theta 0 to pi
As shown in BvU's graph, the region of integration is entirely on the left side of the vertical axis. What is ##\theta## at the upper intersection point? At the lower intersection point? There is also some symmetry you can take advantage of.
 
stolencookie said:
little piece of the cardoid that isn't in the first quadrant
Ambiguous -- in the picture a small piece is missing because I simply didn't grab the full ##\theta## range for the red curve :smile:
 

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