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Vector addition confusion

  1. Jun 2, 2013 #1
    I am stuck on this one:


    According to me, the only correct answers are

    [itex]\vec{r} = \vec{t} - \vec{s} \\ \vec{r} + \vec{s} = \vec{t}[/itex]

    But according to the key, these are also correct

    [itex]\vec{r} + \vec{t} = \vec{s} \\ \vec{s} + \vec{t} = \vec{r} [/itex]

    I honestly do not see how, can somebody please explain?
  2. jcsd
  3. Jun 2, 2013 #2


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    Those are wrong, unless you have some special, weird vector spaces.
  4. Jun 2, 2013 #3


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    However it does look like t - r = s.
  5. Jun 2, 2013 #4


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    Staff: Mentor

    That is another valid equation. t=r+s, r=t-s and s=t-r are equivalent.
  6. Jun 2, 2013 #5
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