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Prove This!

  1. Feb 9, 2005 #1
    (a-b)X(a+b)=2(aXb), where a and b are vectors.

    Thank you.
  2. jcsd
  3. Feb 9, 2005 #2


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    What have you tried so far?

    I would start with the definition of cross multiplication.
  4. Feb 9, 2005 #3
    I tried to set a=<x,y,z> and b=<x1,y1,z1> and expand everything...and the left side became a big mess.
  5. Feb 9, 2005 #4


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    Why don't u multiply exactly what u were given...?I mean there are exactly 4 cross products u'd be getting,when doing it.2 of them are 0...

  6. Feb 9, 2005 #5


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    The cross product is distributive. Use that and some of its other properties to get the answer. No need to fiddle with components.
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