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Homework Help: Find the curvature of the plane curve given by r(t) = (3cost)i + (3sint)j at the poin

  1. Oct 5, 2011 #1
    Find the curvature of the plane curve given by r(t) = (3cost)i + (3sint)j at the point (√(2), √(7) ).

    I know that κ=|r'(t) x r"(t)| / |r'(t)|^3
    However, I believe that you are not allowed to do cross product unless there is an x, y, and z component and this question only has an x and y component.

    In this case, am I supposed to use κ= |T'(t)/r'(t)| instead or use another formula all together?
     
  2. jcsd
  3. Oct 6, 2011 #2

    LCKurtz

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    Re: Find the curvature of the plane curve given by r(t) = (3cost)i + (3sint)j at the

    Just add a 0k to your vector and treat it as 3D if you want to use the cross product.
     
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