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Homework Help: Proof: Principal Moment of Inertia

  1. Nov 6, 2006 #1
    How do i go about proving that none of the principal moments of inertia can exceed the sum of the other two?

    Someone suggested the triangle inequality, but i don't understand how to use it.
  2. jcsd
  3. Nov 6, 2006 #2


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    Homework Helper

    Just write out the definitions:

    [tex]I_x=\int (y^2+z^2)dm[/tex]
    [tex]I_y=\int (x^2+z^2)dm[/tex]
    [tex]I_z=\int (x^2+y^2)dm[/tex]

    and fiddle around with that.
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