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Homework Help: [Dot Product] Vector Proection

  1. Nov 3, 2011 #1
    [Dot Product] Vector Projection

    1. The problem statement, all variables and given/known data

    OA1VY.jpg

    2. Relevant equations

    3Xrpu.jpg

    b1Jy6.jpg

    3. The attempt at a solution

    I am not sure what to do here -- I know that the projection of u onto a "dotted" with w = 0 by definition, but I don't know how to show this.

    X0lLw.jpg

    JldYG.jpg

    added this second part after plugging in for the definition of the projection we derived in class, then simplified. . .
     
    Last edited: Nov 3, 2011
  2. jcsd
  3. Nov 3, 2011 #2
    anyone?
     
  4. Nov 3, 2011 #3

    I like Serena

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    Hi Highway! :smile:

    You have an expression for the projection.
    Can you substitute that (and only that) in the formula you have for w?

    To show that 2 vectors are orthogonal, you need to show that their dot product is zero. That is, that [itex]\vec a \cdot \vec w = 0[/itex].

    What you need to know, is that there are calculation rules for dot products.
    For instance [itex]\vec a \cdot (\vec b+\vec c) = \vec a \cdot \vec b + \vec a \cdot \vec c[/itex].

    Can you simplify the expression for [itex]\vec a \cdot \vec w = 0[/itex]?
     
  5. Nov 3, 2011 #4
    Thanks!! I got it figured out :P

    M0r1c.jpg
     
  6. Nov 3, 2011 #5

    I like Serena

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    Congrats! :wink:
     
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