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Homework Help: The dot product.

  1. Nov 24, 2004 #1
    I'm sorry if this is placed under the wrong section of the forum.

    But i really need help with a problem.

    Well, here it is;

    Find a unit vector that is parallel to the xy-plane and perpendicular to the vector 4i - 3j + k *note* there is a ^ above the ijk.
  2. jcsd
  3. Nov 24, 2004 #2


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    Can you write down an algebraic condition for a vector to be parallel to the xy plane?
    What about for a vector to be perpendicular to 4i-3j+k?
    And for a vector to be a unit vector?
  4. Nov 25, 2004 #3


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    If the vector is parallel to the xy plane, it must be perpendicular to the z-axis. Unit vector k lies on the z-axis. So, if you find a vector that's perpendicular to both unit vector k and your vector, it will solve your problem.

    Whenever you take the cross product of two vectors, the result is perpendicular to both of the original vectors.
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