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Homework Help: 3-dimensional Vector problem.

  1. Mar 12, 2007 #1
    1. The problem statement, all variables and given/known data

    Given the vectors: V1=(3,1,2) and V2=(2,2,-1), find the set of vectors which are coplanar with V1 and V2 and also perpendicular to V3=(-2,1,1). Then Find the members of this set which have length 2-Root-11

    2. Relevant equations

    Dot and cross product

    3. The attempt at a solution

    well, a set of vectors coplanar to v1 and v2 would be V = (x,y,z) = (x',y',z') + rV1 +sV2
    and a vector perpendicular to v3 in the set of vectors coplanar with v1 and v2 is: V X V3.
    But what do i do with the 2-root-11?
    Last edited: Mar 12, 2007
  2. jcsd
  3. Mar 12, 2007 #2


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    Homework Helper

    VxV3 is not necessarily coplanar with V1 and V2. It's just perpendicular to whatever V you choose. Can you think of an expression using a dot product to express V perpendicular to V3? Finally the length of a vector is sqrt(v.v), right?
  4. Mar 12, 2007 #3
    okay, ill try it that way...
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