1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Integrating in polar coordinates (volume)

  1. Mar 28, 2009 #1
    1. The problem statement, all variables and given/known data

    The solid bounded by the parabolids z = 3x^2 + 3y^2 -7 and z = -x^2 -y^2 + 9

    2. Relevant equations

    3. The attempt at a solution

    Ok so i set the two z equations into polar form and came up with 3r^2 = 7 and r^2 = 9
    I thought that r went from (7/3) ^(1/2) to 3 and that theta went from 0 to 2pi.
    I figured the equation to integrate was -4r^2 + 16. (Outer bounds -inner bounds) Anyway, the answer the book gives is different than the two different ways I tried. Just need help setting up the integral...thanks
  2. jcsd
  3. Mar 28, 2009 #2
    This is a 3-D problem; you were given z coordinate values in each case. Work with those.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook