Solving Integration Problem with Double Integral in Polar Coordinates

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In summary, the conversation involves integrating a double integral with the bounds determined by the fact that x^2+y^2 is greater than or equal to 2. The integral is impossible to calculate using cartesian coordinates, so the question is how to do it using polar coordinates. The conversation then moves on to discussing a specific integral in question, which involves a surface and a vector field. The summary also includes the calculations and steps taken to find the solution.
  • #1
JaysFan31
I need to integrate
double integral 2(sqrt(9-x^2-y^2)(-x^2+y^2-2)dxdy with the bounds determined by the fact that x^2+y^2 is greater than or equal to 2.

This integral is impossible to calculate using cartesian coordinates. How would I do it using polar coordinates?
 
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  • #2
[tex] \int \!\!\! \int 2\sqrt{(9-x^2-y^2)(-x^2+y^2-2)}\,dx\,dy [/tex]

[tex] x^2 + y^2 \geq 2 [/tex]

Is that the integral in question?
 
  • #3
That's an infinite region isn't it?
 
  • #4
Yes that's it, the one cepheid wrote.

Well it's obviously part of a problem so here goes:
Let S be the subset of the surface of the sphere x^2+y^2+z^2=9 for which x^2+y^2 is greater than or equal to 2. Let F be the vector field defined by (-y, x, xyz).

Computer double integral(curlF)*ndS where * is the dot product and S is oriented so that the unit normal n to S points away from the enclosed volume.

I have the vector field= -yi+xj+xjzk.
curlF (after calculation)=xzi-yzj+2k
G(x,y,z)=9-z^2-x^2-y^2 and gradG=-2xi-2yj-2zk
Thus, dS=(-2xi-2yj-2zk)dxdy
The dot product of curlF and dS=-2(x^2)z+2(y^2)z-4z
I plug in for z=sqrt(9-x^2-y^2) and I'm in this predicament.
 
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FAQ: Solving Integration Problem with Double Integral in Polar Coordinates

1. What is a double integral in polar coordinates?

A double integral in polar coordinates is a mathematical tool used to find the area under a curved surface in a polar coordinate system. It involves integrating over two variables, typically the radius and the angle, instead of just one in a single integral.

2. How do you convert a double integral in Cartesian coordinates to polar coordinates?

To convert a double integral in Cartesian coordinates to polar coordinates, you first need to express the function in terms of polar coordinates by replacing x and y with their respective polar coordinate equivalents. Then, you need to change the bounds of the integral to correspond to the polar coordinate system.

3. What are the advantages of using polar coordinates in integration problems?

There are several advantages of using polar coordinates in integration problems. One major advantage is that they are better suited for problems involving circular or symmetrical regions. Additionally, they can often simplify the integrand and make the integration process more manageable.

4. How do you solve a double integral in polar coordinates?

To solve a double integral in polar coordinates, you first need to convert it from Cartesian coordinates to polar coordinates. Then, you can use the standard techniques for solving double integrals, such as iterated integration or the use of polar coordinate formulas.

5. What are some common applications of solving integration problems with double integrals in polar coordinates?

Solving integration problems with double integrals in polar coordinates is commonly used in physics, engineering, and other fields to calculate areas, volumes, and moments of inertia for non-Cartesian shapes. It is also used in the study of curves and surfaces in polar coordinate systems.

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