Triple integral from cartesian to spherical coordinates

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Homework Help Overview

The problem involves evaluating a triple integral in spherical coordinates, specifically the integral of the function (x^2+y^2+z^2)^2 over a defined volume. The limits of integration are provided in Cartesian coordinates, and the original poster is seeking assistance in converting these limits to spherical coordinates.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand how to set up the limits for the spherical coordinates, questioning whether the limits for theta should be from 0 to 2π and expressing uncertainty about the limits for phi and p.
  • Some participants suggest that the region corresponds to an octant of a sphere and discuss the implications for the limits of integration.
  • Others question the specific bounds for theta and phi in the context of the first octant and the geometry of the sphere.

Discussion Status

Participants are actively discussing the setup of the integral in spherical coordinates, with some providing visual aids and clarifications about the geometric interpretation of the region of integration. There is a recognition of the need to determine appropriate bounds for theta and phi, but no consensus has been reached on the final setup.

Contextual Notes

Participants note that the integral represents a portion of a sphere in the first octant, and there is an emphasis on visualizing the boundaries and limits of integration in spherical coordinates. The original poster expresses difficulty in visualizing the sphere's boundaries and the corresponding limits.

smashyash
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Homework Statement



evaluate the following triple integral in spherical coordinates::

INT(=B) = (x^2+y^2+z^2)^2 dz dy dx

where the limits are:

z = 0 to z = sqrt(1-x^2-y^2)
y = 0 to z = sqrt(1-x^2)
x = 0 to x = 1

Homework Equations



The only thing I know for sure is how to set up the spherical function:

INT_B = p^6 sin(phi) dp d(theta) d(phi)


The Attempt at a Solution



Now, how do you evaluate the limits??

I assume it's a cylinder so are the theta limits 0 to 2pi?
 
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It looks like an octant of a sphere to me.
 
Dick said:
It looks like an octant of a sphere to me.

Oh, yes. I'm mistaken...

Unfortunately, I still don't know how to finish setting up with new integral...
 
smashyash said:
Oh, yes. I'm mistaken...

Unfortunately, I still don't know how to finish setting up with new integral...

You already have the integral. You just need the bounds.
Which bounds would correspond to the octant of a sphere?
 
Dick said:
This is about as easy as setting up limits in spherical coordinates get. Look up a nice picture of what the coordinates in spherical coordinates look like. Like here http://mathworld.wolfram.com/SphericalCoordinates.html Then picture your octant on top of that.

Thanks you! That's a great visual aid!

I like Serena said:
You already have the integral. You just need the bounds.
Which bounds would correspond to the octant of a sphere?

This is still the trouble I have... visualizing exactly where this sphere is or what it's boundaries are..

I would think that both theta and phi are from 0 to pi/2 and I'm really unsure about p..
 
z= \sqrt{1- x^2- y^2
is equivalent to saying that z is non-negative and that x^2+ y^2+ z^2= 1.
That's the part of the sphere, with center at (0, 0, 0) and radius 1, in the first octant.

Normally, \theta would go from 0 to 2\pi to cover the entire circle in the xy plane. Here, you only want to cover the first quadrant. How should \theta vary?

Normally, \phi would go from 0 to \pi to cover the entire half circle from the positive z-axis to the negative z-axis. Here, you only want to go half way, from the positive z-axis to z= 0. How should \phi vary?

Of course, \rho goes from 0 out to the sphere of radius 1.
 

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