Triple Integral problem (maybe using spherical coordiantes)

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SUMMARY

The discussion focuses on solving a triple integral of the function f(x, y, z) = -4x + 6y over a solid defined by a cone and a sphere in the first octant. The solid is bounded by the planes x = 0 and y = x * sqrt(22/3), contained within a sphere of radius 13 and a cone with a top radius of 5. The user explores the use of spherical coordinates but is advised to switch to cylindrical coordinates for better symmetry, with the integration limits defined as θ from 0 to 2π, r from 0 to 5, and z from √(22/3)r to √(169 - r²).

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batmankiller
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Homework Statement



Integrate the function f(xyz)=−4x+6y over the solid given by the "slice" of an ice-cream cone in the first octant bounded by the planes x=0 and y=x*sqrt(22/3) and contained in a sphere centered at the origin with radius 13 and a cone opening upwards from the origin with top radius 5.

Homework Equations


x^2+y^2+z^2=p(row)
x=p(sinf(fie)*cost(theta)
y=p*sinfsint

The Attempt at a Solution


So I changed function 6y-4x into the terms of spherical coordinates. While i attempted to find the limits of the integral, I'm not sure if my drawing is correct:
masth.png


But I assumed it meant that the region had to be inside the cone such that it was in the first octet (since it's bounded by x=0 which is the yz plane --NOT SHOWN IN PICTURE), but I'm not sure how the ice cream part has to do with this...
Could someone just explain to me what the trace part means and also explain if my drawing is right, I have no idea what inside the circle and the cone means..
 
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I would recommend cylindrical coordinates because there is more cylindrical symmetry than spherical symmetry. If you alter the coordinates so that the axis of the cone is along the z-axis then you have cone itself as given by z= \sqrt{22/3}r and the sphere by r^2+ z^2= 169. To integrate over that, \theta goes from 0 to 2\pi, r goes from 0 to 5, and z goes from \sqrt{22/3}r to \sqrt{169- r^2}. Of course, now the integrand is f(x, y, z)= -4x+ 6z= -4rcos(\theta)+ 6z since we have swapped y and z.
 
Oh so you do suggest that I change the cone? altering it doesn't mess with the problem?
i still can't seem to integrate this =[
 
Last edited:

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