Parametric Equation intersection and area

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SUMMARY

The discussion focuses on finding the area between the curves defined by the parametric equations r=2sin(θ) and r=2sin(2θ) for the interval 0 ≤ θ ≤ π/2. The intersection point is determined to be θ=π/3, where the two curves meet. The area is calculated by setting up integrals for sin(θ) and 2sin(2θ) from π/3 to π/2. The initial calculation yielded an area of 1/2, which was later identified as incorrect due to potential errors in the limits of integration.

PREREQUISITES
  • Understanding of polar coordinates and parametric equations
  • Knowledge of trigonometric identities, specifically sin(2θ)
  • Familiarity with integral calculus, particularly definite integrals
  • Experience with area calculations in polar coordinates
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  • Review the process of finding intersections of polar curves
  • Study the application of definite integrals in polar coordinates
  • Learn about the area calculation between two polar curves
  • Explore trigonometric identities and their applications in calculus
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Students studying calculus, particularly those focusing on polar coordinates and area calculations, as well as educators seeking to clarify concepts related to parametric equations and integration techniques.

BradyK
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Homework Statement


Given the curves r=2sin(θ) and r=2sin(2θ), 0 ≤ θ ≤ pi/2, find the area of the region outside the first curve and inside the second curve


Homework Equations


obviously set up an intersection to see where the two meet, then subtract the circle equation from the rose equation.


The Attempt at a Solution



First setting up the intersection:
2sin(θ) = 2sin(2θ)
sin(θ) = sin(2θ)
sin(θ) = 2sin(θ)cos(θ)
1 = 2cos(θ)
1/2 = cos(θ)
pi/3 = θ

so then setting up the integrals, you have sin(θ) dθ bound by pi/3 to pi/2 minus 2sin(2θ) dθ bound by pi/3 to pi/2

working through it, I was able to get an answer of 1/2, but entering it in, the answer turned out to be incorrect. Any help here would be greatly appreciated, thank you.
 
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BradyK said:
so then setting up the integrals, you have sin(θ) dθ bound by pi/3 to pi/2 minus 2sin(2θ) dθ bound by pi/3 to pi/2

working through it, I was able to get an answer of 1/2, but entering it in, the answer turned out to be incorrect. Any help here would be greatly appreciated, thank you.

Hi BradyK! Welcome to PF! :smile:

You should recheck those limits. You are looking for the area outside the first curve r=2sin(θ) and inside the second curve r=2sin(2θ).
 

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