Help me setup and solve double integral in polar coord.

In summary, the region between the sphere x^2+y^2+z^2=3 and the upper sheet of the hyperboloid z^2=x^2+y^2+1 has a curve of intersection that is a circle of radius 1. Using polar coordinates, the double integral can be set up as (3-x^2-y^2)-(x^2+y^2+1) which simplifies to 2-2r^2. The bounds for the integral are theta from 0 to 2pi and r from 0 to 1. After integrating, the volume of the region is pi.
  • #1
RJLiberator
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Homework Statement


The region between sphere x^2+y^2+z^2=3 and the upper sheet of the hyperboloid z^2=x^2+y2+1.

Homework Equations

The Attempt at a Solution



Curve of intersection: We set the two equations equal to each other and find x^2+y^2=1, a circle of radius 1 is the curve of intersection.
I then drew the graph of the two elements here.

Now, I need to set up the actual double integral.
I know my bounds: theta from 0 to 2pi and r from 0 to 1.

I know that using polar coordinates I have to use r*dr*d(theta).

My problem is, I don't know how to set up the rest of the integral. I think it has something to do with f(r,theta)-g(r,theta) but I've been trying various things and nothing seems to be clear/working out.

I think I should do (3-x^2-y^2) - (x^2+y^2+1) as that seems to be the correct order, but how do I switch this to polar coordinates :/.
 
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  • #2
After re-looking at some conversion formula's, I may have solved it:

So we do (3-x^2-y^-2)-(x^2+y^2+1) which is upper-lower and we get 2-2x^2-2y^2.
We then convert to polar coordinates and simplify the sin^2(theta)+cos^2(theta) so that we get: 2-2r^2
We can now use this in the integral with the bounds that I posted above, we multiply both by r: 2r-2r^3 and then we simply integrate.
The answer should be V = pi.

:)
 

1. What is a double integral in polar coordinates?

A double integral in polar coordinates is a type of integration that is used to find the area under a curve in a polar coordinate system. It involves integrating a function over a region in the polar plane, which is defined by a combination of polar coordinates.

2. How do I set up a double integral in polar coordinates?

To set up a double integral in polar coordinates, you first need to identify the region of integration in the polar plane. This can be done by drawing a graph and determining the boundaries of the region. Then, you need to convert the integrand into polar form and set up the integral using the appropriate limits of integration.

3. What is the process for solving a double integral in polar coordinates?

The process for solving a double integral in polar coordinates involves converting the integrand into polar form, setting up the integral with the appropriate limits, and then evaluating the integral using integration techniques such as substitution or integration by parts.

4. How do I know if I need to use a double integral in polar coordinates?

You will need to use a double integral in polar coordinates when you are trying to find the area under a curve in a polar coordinate system. This is typically the case when the region of integration is defined in polar coordinates and the integrand is also in polar form.

5. Are there any common mistakes to avoid when setting up and solving a double integral in polar coordinates?

Some common mistakes to avoid when setting up and solving a double integral in polar coordinates include forgetting to convert the integrand into polar form, choosing the incorrect limits of integration, and making errors in the integration process. It is important to double check your work and be familiar with the conversion between rectangular and polar coordinates.

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