Find appropriate parametrization to find area bounded by a curve

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SUMMARY

The discussion focuses on finding an appropriate parametrization to calculate the area bounded by the curve defined by the equation x2/5 + y2/5 = a2/5. The suggested parametrization involves using polar coordinates, specifically x = r cos(θ) and y = r sin(θ). The Jacobian determinant |J| is identified as r, which leads to the differential area element dx dy = |J| dr dθ. The main challenge lies in determining the correct limits of integration for the double integral required to compute the area.

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Problem:

Use an appropraite parametrization x=f(r,\theta), y=g(r,\theta) and the corresponding Jacobian such that dx \ dy \ =|J| dr \ d\theta to find the area bounded by the curve x^{2/5}+y^{2/5}=a^{2/5}

Attempt at a Solution:

I'm not really sure how to find the parametrization. Once I have that, calculating the Jacobian is simple. Then all that's left is computing a double integral. Right?
 
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wifi said:
Problem:

Use an appropraite parametrization x=f(r,\theta), y=g(r,\theta) and the corresponding Jacobian such that dx \ dy \ =|J| dr \ d\theta to find the area bounded by the curve x^{2/5}+y^{2/5}=a^{2/5}

Attempt at a Solution:

I'm not really sure how to find the parametrization. Once I have that, calculating the Jacobian is simple. Then all that's left is computing a double integral. Right?

Hint: Your parametrization hints at polar co-ordinates.

##x = rcos\theta, y = rsin\theta##
 
But if I use ##x=rcos\theta## and ##y=rsin\theta##, then I have ##dx=rd\theta## and ##dy=rd\theta##. Also ##|J|=r##. However we want ##dx \ dy=|J|dr \ d\theta##.

Using ##x=rcos\theta## and ##y=rsin\theta##, then the curve is given by (rcos\theta)^{\frac{2}{5}}+(rsin\theta)^{\frac{2}{5}}=a^{\frac{2}{5}}

So to find the area bounded by this curve we want to perform a double integral. I'm just confused on setting it up. Now that we're in terms of ##r## and ##\theta##, how do we figure out the limits of integration for the given curve?
 
Last edited:

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