Finding the Area Inside Two Polar Curves

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Homework Help Overview

The problem involves finding the area of the region that lies inside two polar curves: \( r^2 = 2 \sin(2\theta) \) and \( r = 1 \). The context is centered on polar coordinates and area calculations in calculus.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the points of intersection found at \( \frac{\pi}{12}, \frac{5\pi}{12}, \frac{13\pi}{12}, \frac{17\pi}{12} \) and express confusion about setting up the integral correctly to find the area that lies inside both curves. There are suggestions about considering the area of one petal of the rose curve and subtracting the area of the outer curve from the inner curve, then multiplying by two. Another participant emphasizes the need to break the integral into appropriate pieces as the inner curve changes.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of how to set up the area calculation. Some guidance has been offered regarding the setup of the integral, but there is no explicit consensus on the final approach yet.

Contextual Notes

Participants mention the visual representation of the curves, noting that one of the figures resembles a rose with two petals, and there is a focus on the area that lies inside both curves, excluding the parts of the petals that extend beyond the circle.

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Homework Statement



Find the area of the region that lies inside both curves: r^2=2sin2θ, r=1

Homework Equations


A=integral 1/2 (f(θ)^2-g(θ)^2) from a to b

The Attempt at a Solution


I found the points of intersection as pi/12,5pi/12,13pi/12,17pi/12 but the fact that its inside both of them is throwing me off on setting it up. I have also sketched it but that hasn't really helped. Any help would be greatly appreciated
 
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aces9113 said:

Homework Statement



Find the area of the region that lies inside both curves: r^2=2sin2θ, r=1

Homework Equations


A=integral 1/2 (f(θ)^2-g(θ)^2) from a to b

The Attempt at a Solution


I found the points of intersection as pi/12,5pi/12,13pi/12,17pi/12 but the fact that its inside both of them is throwing me off on setting it up. I have also sketched it but that hasn't really helped. Any help would be greatly appreciated
One of the figures is what is called a rose with two petals. To me it looks like a propeller with two blades. The blades are in the first and third quadrants.

The region whose area you are supposed to find is everything that lies inside both curves. IOW, the parts of the propeller blades that extend beyond the circle aren't included.
 
I understand that based on the sketch. But would i possibly do the area of one propeller minus (area of the outside curve-the inside curve) and then multiply that by two? I'm lost when it comes to setting this one up
 
Adding to what Mark44 has said, remember that r goes from 0 to the inner curve as θ moves around the circle. And the inner curve changes so you have to break the integral up into appropriate pieces.
 
could someone please check my answer? i got 2 +pi/3 - sqrt(3)
 
aces9113 said:
could someone please check my answer? i got 2 +pi/3 - sqrt(3)

Good job. That's what I get too.
 

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