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A little help, please

  1. Jan 30, 2006 #1
    Hi, I'm Xairylle and I need a little help with this. I think it's kind of basic electromagnetics stuff but I don't know how this goes given that all I've got is a problem nothing else. I can't seem to get any of it and... it's not homework.

    1. Express each of the given points into its equivalent vector
    a) A(2,1,-5)
    b) A(1,4,6) B(5,-3,0)

    2. Find the lengths of the medians of the given triangles ABC
    a) A(2,1,3) B(3,-1,-2) C(0,2,-1)

    I need solutions and answers since I really can't understand. Please help if it's not too much trouble. Thank you.
  2. jcsd
  3. Jan 30, 2006 #2


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    while this may not be homework, it is the sort of question which is very common in homework.
  4. Jan 30, 2006 #3
    Each number in the bracket of three numbers is just representing a different dimension. E.g. [tex](l, w, h)[/tex]
  5. Jan 31, 2006 #4


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    If by "equivalent vector" you mean what I would call "position vector" it is the vector pointing from the origin, (0, 0, 0), to the given point, (x, y, z) and is written as xi+ yj+ zk.
  6. Feb 1, 2006 #5
    First of all, you must know 2 points (usually given) in order to create the specific vector. If so, the vector's coordinates are given by the coordinates of the second point minus the coordinates of the first.
    For example, find the coordinates of the vector AB where A(1,-2,4) and B(2,2,-1).
    It's obvious that AB(2-1,2+2,-1-4) ---> AB(1,4,-5)

    In your first exercise, the position vector is asked. The position vector can be created by only knowing one point. The other point is always the origin point O(0,0,0).
    Here are your answers:
    a) OA(2-0,1-0,-5-0) ----> OA(2,1,-5)
    b)AB(5-1,-3-4,0-6) ---->AB(4,-7,-6)

    In your second exercise, the length of a vector is asked.
    For example, if AB(2,-3,-1) you can find the length by:

    squareroot[2^2 + (-3)^2 + (-1)^2]=squareroot(4 + 9 +1)= =squareroot(14)

    Good luck https://www.physicsforums.com/images/smilies/smile.gif [Broken]
    Last edited by a moderator: May 2, 2017
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