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Homework Help: Linear Algebra: Dot Product and Orthogonality

  1. Sep 27, 2011 #1
    This is from my homework, I was moving along nicely until I hit this problem, (there's another just like it right after this). I can't find reference for solving this in the chapter Im looking at. The answer is in the back of the book….-2911. Can someone explain this to me?


    [tex]
    ||\mathbf{u}|| = 5\, and\: ||\mathbf{v}|| = 7; \,find\: (3\mathbf{u} - 8\mathbf{v}) \circ (3\mathbf{u} + 8\mathbf{v}).
    [/tex]


    I know that [itex]||\mathbf{u}||[/itex] is just the length of the vector, etc. I just don't know where to go from there.
     
  2. jcsd
  3. Sep 27, 2011 #2

    lanedance

    User Avatar
    Homework Helper

    try expanding the dot product using its linear properties, should simplify a heap
     
  4. Sep 27, 2011 #3
    You were right. Solved it first go after that. Thank you.
     
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