Volume in cylindrical coordinates

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SUMMARY

The discussion focuses on calculating the volume bounded by the surfaces defined by the equations x² + y² + z² = 2 and z = x² + y² using cylindrical coordinates. The correct transformation yields z = √2 - r² and z = r², with the integration limits set as z from r² to √2 - r², r from 0 to √2, and θ from 0 to 2π. The participant encountered a negative volume upon evaluation, indicating a potential error in the setup or limits of the integral.

PREREQUISITES
  • Cylindrical coordinates conversion
  • Understanding of triple integrals
  • Knowledge of volume calculation in multivariable calculus
  • Familiarity with surface equations and their intersections
NEXT STEPS
  • Review the method for converting Cartesian coordinates to cylindrical coordinates
  • Study the evaluation of triple integrals in cylindrical coordinates
  • Examine the geometric interpretation of the surfaces involved
  • Learn about the conditions for determining volume in multivariable calculus
USEFUL FOR

Students studying multivariable calculus, particularly those focusing on volume calculations in cylindrical coordinates, as well as educators looking for examples of common pitfalls in integral evaluation.

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Homework Statement



Find the volume using cylindrical coordinates bounded by:

x2+y2+z2=2 and

z = x2+y2

Homework Equations



Converting to cylindrical coordinates:
z = √2-r2 and

z = r2

The Attempt at a Solution



I figured z would go from r2 to √2-r2
r from 0 to √2
and θ from 0 to 2∏.
However, when I evaluate the integral I get a negative volume. (And no, I did not forget to multiply by an extra r)

I have no idea where I've gone wrong.
 
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physics&math said:

Homework Statement



Find the volume using cylindrical coordinates bounded by:

x2+y2+z2=2 and

z = x2+y2

Homework Equations



Converting to cylindrical coordinates:
z = √2-r2 and

z = r2

The Attempt at a Solution



I figured z would go from r2 to √2-r2
r from 0 to √2
and θ from 0 to 2∏.
However, when I evaluate the integral I get a negative volume. (And no, I did not forget to multiply by an extra r)

I have no idea where I've gone wrong.

What is the x,y equation of the intersection of your two surfaces? Are you sure you copied the problem correctly?
 

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