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Parameterization problem help

  1. May 2, 2009 #1
    1. The problem statement, all variables and given/known data

    Parameterize C, the line segment from the point (1,4,-2) to the point (6,7,-2).


    2. Relevant equations



    3. The attempt at a solution

    I got:

    [tex] \vec{r}(t) = 6+5t \vec{i} + 7+3t \vec{j} + 2 \vec{k} [/tex]

    for some reason webassign tells me it's wrong
     
  2. jcsd
  3. May 2, 2009 #2

    tiny-tim

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    Hi -EquinoX-! :smile:
    erm :redface: … it's minus 2k, isn't it ? :wink:

    (and some brackets would be a good idea :rolleyes:)
     
  4. May 2, 2009 #3
    Re: parameterization

    yes it's -2k, I just mistyped it.. still gives me the wrong answers
     
  5. May 2, 2009 #4
    Re: parameterization

    well, look at it this way.

    let r_o=<1,4,-2>, and let u=<5,3,0>. if P1(1,4,-2) and P2(6,7,-2) then as you can see
    u=P1P2
    Let, r=<x,y,z>

    then in general the equation of the line that passes through P1 and whose diercition is along the vector u, is

    r=r_o+tu =>

    r=i+4j-2k+5ti+3tj=(1+5t)i+(4+3t)j-2k

    where 0=<t=<1.
     
  6. May 3, 2009 #5

    tiny-tim

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    In that case, either it doesn't like your absence of brackets, or since it asked for "the line segment from …", it probably expects t to be increasing in that direction. :wink:
     
  7. May 3, 2009 #6

    HallsofIvy

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    Re: parameterization

    that doesn't even make sense. You are adding numbers to vectors. Do you mean
    [tex]\vec{r}(t)= (6+ 5t)\vec{i}+ (7+ 3t)\vec{j}- 2\vec{k}[/tex]
     
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