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How can I prove it?

  1. Oct 31, 2009 #1
    1. The problem statement, all variables and given/known data

    How can I prove this theorem? A, B, C and D are vectors.

    (A[tex]\times[/tex]B).(C[tex]\times[/tex]D)=(A.C)(B.D)-(A.D)(B.C)

    2. Relevant equations

    A[tex]\times[/tex]B=ABsin([tex]\theta[/tex]) and A.B=ABcos([tex]\theta[/tex])

    3. The attempt at a solution

    Please help me solve it.
     
  2. jcsd
  3. Oct 31, 2009 #2
    There's one more relevant equation. As a hint, think of AxB as an additional vector V.
     
  4. Oct 31, 2009 #3
  5. Oct 31, 2009 #4
    yeah I'm sure that this solves the problem, and it seems obvious, so thank u very much, but do u know an easier way or a cleaner (lol) way to prove it.
     
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