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Homework Help: Prove The Vector Equation

  1. Jan 21, 2013 #1
    1. The problem statement, all variables and given/known data

    Prove llu+vll2 + llu-vll2 =2llull2 + 2llvll2

    2. Relevant equations

    I am thinking I need to use some dot, or cross products.

    3. The attempt at a solution

    I just do not know where to start.
  2. jcsd
  3. Jan 21, 2013 #2


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    Gold Member

    Use what you know for finding the length of a vector (in terms of a dot product)and the associativity of the dot product.
  4. Jan 21, 2013 #3
    What do you mean by that?
  5. Jan 21, 2013 #4


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    Science Advisor
    Homework Helper

    ||a||^2=a.a, use that.
  6. Jan 21, 2013 #5
    Ohhh thanks! Now I get it.
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