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Vector squared

  1. May 19, 2007 #1
    If I have (a + b)^2 = c, where a and b are vectors, is c = a^2 + 2(a . b) + b^2, or simply is c=a^2 +b^2 + 2ab?

    My motivation behind considering the former is that q^2 = q.q, however my motivation behind considering the latter is that if I have q^2=c then it does not matter whether q ia a vector or not, c is the same...

    :/
     
  2. jcsd
  3. May 19, 2007 #2

    malawi_glenn

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    Yes the a b should be dot product.

    |a|*|b|cos(w) w is angle between a and b.

    so: c = (a + b) ^2 = [a|^2 + |b|^2 + 2|a|*|b|cos(w)
     
  4. May 19, 2007 #3
    thanks malawi :)
     
    Last edited: May 19, 2007
  5. May 19, 2007 #4

    malawi_glenn

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    np good luck!

    ps. this is not a home work question in "Advanced physics" , but in precalclus maths hehe
     
  6. May 19, 2007 #5
    Oh yeah you are right, sorry about that. I didn't realise there was such a section in the forums :) thanks for the heads up.
     
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