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Parameterization problem help

  • Thread starter -EquinoX-
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  • #1
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Homework Statement



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


Homework Equations





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
 

Answers and Replies

  • #2
tiny-tim
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Hi -EquinoX-! :smile:
Parameterize C, the line segment from the point (1,4,-2) to the point (6,7,-2).

I got:

[tex] \vec{r}(t) = 6+5t \vec{i} + 7+3t \vec{j} + 2 \vec{k} [/tex]
erm :redface: … it's minus 2k, isn't it ? :wink:

(and some brackets would be a good idea :rolleyes:)
 
  • #3
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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:)
yes it's -2k, I just mistyped it.. still gives me the wrong answers
 
  • #4
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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.
 
  • #5
tiny-tim
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… still gives me the wrong answers
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:
 
  • #6
HallsofIvy
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Homework Helper
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Homework Statement



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


Homework Equations





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
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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