Find the volume of the region inside the sphere and cylinder?

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Homework Help Overview

The problem involves finding the volume of the region inside a sphere defined by the equation x²+y²+z²=9, specifically under the xy-plane, and also inside a cylinder defined by x²+y²=5. The context suggests the use of integrals, potentially in cylindrical or spherical coordinates.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the appropriate coordinate system to use, with suggestions leaning towards cylindrical coordinates to simplify the integration process. There are questions about the limits for r and z in cylindrical coordinates, as well as clarifications regarding the specific portion of the sphere being considered.

Discussion Status

The discussion is active, with participants providing hints and suggestions regarding the setup of the integral. There is acknowledgment of the need to clarify the limits of integration, and some participants express gratitude for the guidance offered. However, there is no explicit consensus on the final setup of the integral.

Contextual Notes

There is a mention of a potential misunderstanding regarding whether the problem asks for the top or bottom portion of the sphere, which could affect the limits of integration. Additionally, the original poster indicates uncertainty about how to set up the integral correctly.

khfrekek92
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Homework Statement



Find the volume of the region inside the sphere x^2+y^2+z^2=9, under the xy-plane, and inside the cylinder x^2+y^2=5.

Homework Equations



Need to use integrals in eaither cylindrical or spherical I'm guessing?

The Attempt at a Solution



I've graphed it and I know what region I'm evaluating, but I don't know how to set up the integral.. Thanks for any help!
 
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welcome to pf!

hi khfrekek92 ! welcome to pf! :smile:

(try using the X2 icon just above the Reply box :wink:)

i'd use cylindrical (rather than spherical), because then there's no tricky angle integration :rolleyes:

can you describe in words what the limits are on cylindrical r and z in this case? :wink:
 
Thank you so much! :) And thanks for that useful hint too haha ;)
P.S. The question actually asks for the top portion of this sphere instead of the bottom, soooo... so I'm guessing I would do the triple integral (rdzdthetadr) with z=[0,sqrt(9-r^2)], theta=[0,2pi], and r=[0,sqrt5] ?
 
Thank you so much! :) And thanks for that useful hint too haha ;)
P.S. The question actually asks for the top portion of this sphere instead of the bottom, soooo... so I'm guessing I would do the triple integral (rdzdthetadr) with z=[0,sqrt(9-r^2)], theta=[0,2pi], and r=[0,sqrt5] ?
 
khfrekek92 said:
… I would do the triple integral (rdzdthetadr) with z=[0,sqrt(9-r^2)], theta=[0,2pi], and r=[0,sqrt5] ?

yup! :smile:
 
Yay! Thanks so much tiny-tim! :)
 

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