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Point dividing a line segment (externally)

  1. Feb 13, 2014 #1
    I am just not able to connect this concept with my mind,i mean how is it possible to divide a line externally when the point is beyond the line..can anyone explain it intuitively in simple terms kindly? I am not able to grasp it clearly
  2. jcsd
  3. Feb 13, 2014 #2


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    Science Advisor

    You need a precise definition.
  4. Feb 13, 2014 #3
    no,actually I need an intuitive look into the concept maybe...
  5. Feb 13, 2014 #4
    What mathman is saying:
    It's not clear what your original post means. If you want some guidance, being more precise will help.
  6. Feb 14, 2014 #5
    I think i was quite precise sir...
    There is an idea in my text book regarding "point dividing a join of two points in a given ratio" so there in it is written if the point which divides the join of two points,lies beyond the join say AB...then it actually divides the points in ratios "externally"...i could not grasp this idea i mean how is it possible that a line divides in ratio externally
  7. Feb 14, 2014 #6


    Staff: Mentor

    This is not at all clear, possibly as a result of being translated to English from some other language.

    I think I understand part of it - "point dividing a join of two points in a given ratio". I infer that "join of two points" in your book means the line segment between the two points. If we call the two points A and B, we can call this line segment AB. If P is a point on this line segment, it divides the line segment into two parts that are in some ratio. For example, if P is located at 1/3 of the distance from A to B, then the ratio of AP to PB is 1:2 or 1/2.

    With regard to the part about external ratios, I can only guess as to what is meant. For simplicity, let's assume that the points are on the real line, with A at 1 and B at 3. So the line segment AB lies between 1 and 3. If P is at 4, then |AP| = 3 and |PB| = 1. So the ratio of the two line segments is 3:1, and P is a point that is external to AB. Is this anywhere close to what your book is talking about?
  8. Feb 14, 2014 #7
    Yes thanks this is what i was talking About,i couldn't grasp that concept of having a ratio when the point which is dividing the line lies at,say in your case,4 on real line...kindly help me through it
  9. Feb 14, 2014 #8


    Staff: Mentor

    What part of my explanation did you not understand?
  10. Feb 14, 2014 #9
    Actually in my book it talks about external ratio of the same line (AB in your case) and the point which divides them in some ratio k:k, lies beyond that line..I couldn't grasp it how it is an "external" ratio,i mean that would make it completely different (TO me IMHO and i an dumb TBH),it would sense like ratio b/w line AP and BP...and not like the ratio b/w A(a point) and B(same point)...BUT...wait..aah now i got that...thank you btw :) i got the idea of having ratio of the line...i was actually focusing more on "dividing thing" and was constantly thinking that it is only possible when the point which divides them lies "only" b/w them..now i got that.. thank you mate :)
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