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3d-Vector question

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

    pbul0.png

    I'm confused ,


    here's ... my attempt..

    all I know so far is the

    the k component would be 5...
    I have no idea what to do with the i and j
     
    Last edited: Apr 22, 2013
  2. jcsd
  3. Apr 22, 2013 #2

    tiny-tim

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    hi lionely! :smile:
    drop perpendiculars DP and EQ onto the base …

    where are P and Q in relation to ABCD ? :wink:
     
  4. Apr 22, 2013 #3

    SteamKing

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    Hint: Assume DE is located such that its midpoint is positioned directly over the intersection of the base diagonals OB and AC.
     
  5. Apr 22, 2013 #4
    Hmm is DE is assumed to be at the mid point then.. for the j component that would be 4j

    but the i? ... umm is it like the base below DE is 8 because DE is 6cm and OA is 14? so 14-6?
     
  6. Apr 22, 2013 #5
    when I dropped the perpendiculars they ended up being at the midpoints of the widths of the base
     
  7. Apr 22, 2013 #6
    You had your answer in this post, but didn't realize it. 14 - 6 = 8, and this difference is split evenly between between the two sides. So the i component is 4.
     
  8. Apr 23, 2013 #7

    tiny-tim

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    hi lionely! :smile:

    (just got up :zzz:)
    (we'll call them P and Q)

    ok … so the next line in your proof would be to say what the distance PQ is

    and then you can compare that with the length of the base :wink:
     
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