Convert to cylindrical coordinates

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Homework Help Overview

The discussion revolves around converting a triple integral from Cartesian to cylindrical coordinates. The original integral involves variables x, y, and z, and the participants are exploring the appropriate limits and transformations for the cylindrical coordinate system.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the limits of integration for the angle theta, questioning whether it should range from 0 to pi or 0 to pi/2 based on the graph of the region described.

Discussion Status

There is an ongoing exploration of the correct limits for theta, with some participants affirming the need to reconsider the original integral's constraints. Guidance has been offered regarding the interpretation of the first octant and the behavior of x and y in the original setup.

Contextual Notes

Participants are considering the implications of the original integral being defined in the first octant, which affects the limits for theta. There is a focus on ensuring that the transformation to cylindrical coordinates accurately reflects the geometry of the region involved.

caliguy
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Evaluate by changing to cylindrical coordinates

[tex]\int[/tex] from 0 to 1 [tex]\int[/tex] from 0 to (1-y^2)^1/2 [tex]\int[/tex] from (x^2+y^2) to (x^2+y^2)^1/2 (xyz) dzdxdy

I came to an answer of integral from 0 to pi integral from 0 to 1 integral from r^2 to r (rcos[tex]\theta[/tex]rsin[tex]\theta[/tex]z) r dzdrd[tex]\theta[/tex]
Is this the correct answer?
 
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Hello Caliguy. Click on the expression below to see how to post it so it is readable in tex:

[tex]\int_0^1 \int_0^{\sqrt{1-y^2}}\int_{x^2+y^2}^{\sqrt{x^2+y^2}}xyz\ dzdxdy[/tex]

This looks like a first octant integral. Check your [itex]\theta[/itex] limits.
 
To me they seem right, doesn't theta go from zero to pi? after graphing it it looks like a half a circle... maybe I'm overlooking something?
 
Neither x nor y get negative in your original integrals.
 
So theta only goes from 0 to pi/2 right?
 
caliguy said:
So theta only goes from 0 to pi/2 right?

Yes.
 

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