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Vector problem

  1. May 22, 2005 #1
    Hi I was wondering if anyone could help me with this problem:


    In my textbook it says the answer is 1/2(p-q) but I don't understand how that answer is acheived. Any help would be appreciated.

    Many thanks.
  2. jcsd
  3. May 22, 2005 #2


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    Consider the triangle PMQ.Can u express [itex] \vec{p} [/itex] in terms of [itex] \vec{PM} [/itex] and [itex]\vec{MQ} [/itex]...?

    And the same for the other triangle...

    What relation is there between [itex]\vec{PM}[/itex] and [itex]\vec{MR}[/itex] ?

  4. Jun 16, 2005 #3
    In triangle PMQ [itex] \vec{p} [/itex] = [itex] \vec{PM} [/itex] + [itex] \vec{MQ} [/itex].

    Also [itex]\vec{PM}[/itex] = [itex]\vec{MR}[/itex] as in they're the same distance. Could anyone explain how I get the answer please? As my test is now tomorrow :smile:
  5. Jun 16, 2005 #4


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    The way i see it

    [tex]\left\{\begin{array}{c}\vec{MQ}+\vec{PM}=\vec{p}\\ \vec{MQ}+\vec{q}=\vec{MR} \end{array} \right [/tex]

    Now add the 2 eqns.

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