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Homework Help: Vector Equations for line passing through a point

  1. Sep 1, 2011 #1
    Hi,

    I am a bit confused... I don't understand what is happening, I can't picture it:

    Find a vector equation for the line passing through the point 4,3 and parallel to the vector i - 2j.

    If r = p +t (q-p)

    I only have one point, how can I use the fact it is parallel to help me? Point Q must be as such that the dot product of q - p and i - 2j must equal the magnitude of q - p * the magnitude of i - 2j?

    Any help is appreciated

    Thanks,
    Peter
     
  2. jcsd
  3. Sep 1, 2011 #2

    LCKurtz

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    Gold Member

    The vector equation of a line through (a,b) in the direction D = <c,d>is

    <x,y> = <a,b> + t<c,d>

    All you need is a point and a direction vector, which you have given.
     
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