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Line Segment

  1. Feb 23, 2009 #1
    1. The problem statement, all variables and given/known data

    Find the directed line segment joining (1,1,1) to (1,3,1)

    2. Relevant equations



    3. The attempt at a solution

    (1,1,1) + (0,2,0)t is that correct?
     
  2. jcsd
  3. Feb 23, 2009 #2

    Hurkyl

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    Is it a directed line segment?
    Does it start at (1,1,1)?
    Does it end at (1,3,1)?

    If so, then it's correct.
     
  4. Feb 23, 2009 #3

    HallsofIvy

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    Notice the "start and stop". You will need conditions on t as well as, for the "directed" part, something like "as t goes from ___ to ___".
     
  5. Feb 23, 2009 #4
    you mean like this:

    for all t [tex]\rightarrow \Re[/tex]

    or what im trying to say is that for all t that are real numbers (couldn't find the symbol for it; looks like a small 'e')
     
  6. Feb 23, 2009 #5

    HallsofIvy

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    No, the whole point is that t cannot be "all real numbers". That could give the entire line, not the line segment. And you still haven't dealt with the "directed" part. Do you understand the difference between a line segment and a line? Do you understand what a directed line or directed line segment is?
     
    Last edited: Feb 24, 2009
  7. Feb 23, 2009 #6
    [tex]0 \leq t \leq 1[/tex]
     
  8. Feb 24, 2009 #7

    HallsofIvy

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    Okay, that gives the "segment". Now what about the "directed" part? Unfortunately, your original statement of the problem doesn't give a direction. You just said "the directed line segment joining (1,1,1) to (1,3,1)" which does not state a direction. Is the direction from (1, 1, 1) to (1, 2, 1) or from (1, 2, 1) to (1, 1, 1)?
     
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