-12.5.2 Find Parametric eq for line segment from (-2,18,31) to (11,-4,48)

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Discussion Overview

The discussion revolves around finding the parametric equations for a line segment connecting the points (-2, 18, 31) and (11, -4, 48). The scope includes mathematical reasoning and technical explanation related to vector representation and parametric equations.

Discussion Character

  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant expresses uncertainty about how to begin the problem, referencing a book example.
  • Another participant calculates the direction vector as $v = (11,-4,48)-(-2,18,31) = (13,-22,17)$ and proposes the parametric equation $r(t) = (-2,18,31) + (13,-22,17)t$.
  • A subsequent participant questions whether the provided equation is sufficient, indicating an expectation for more detailed steps.
  • A later reply outlines the general form of parametric equations for a straight line and suggests using $t = 0$ and $t = 1$ for the endpoints. They derive the equations: $x = -2t + 13$, $y = -22t + 18$, and $z = 17t + 31$, while checking the endpoints for correctness.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the sufficiency of the initial response, as one participant seeks more detailed steps while another provides a complete derivation of the parametric equations.

Contextual Notes

There are no explicit limitations noted, but the discussion reflects varying expectations regarding the level of detail in the solution process.

karush
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Find Parametric eq for line segment from (-2,18,31) to (11,-4,48)
ok not sure how to start on this the book example is in the spoiler

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direction vector, $v = (11,-4,48)-(-2,18,31) = (13,-22,17)$

$r(t) = (-2,18,31) + (13,-22,17)t$
 
Parametric equations for a straight line are of the form
x= at+ b
y= ct+ d
z= et+ f

We can take t to be any numbers we t to be whatever we like at the given points. I think it simplest to take t to be 0 and 1.

If t= 0 at (-2,18,31) then a(0)+ b= -2 so b= -2, c(0)+ d= 18 so d= 18, and e(0)+ f= 31 so f= 31.

If t= 1 at (11,-4,48) then a(1)+ b= a- 2= 11 so a= 13, c(1)+ d=c+ 18= -4 so c= -22, and e(1)+ f= e+ 31= 48 so e= 17.

x= -2t+ 13
y= -22t+ 18
z= 17t+ 31.

Check; if t= 0, (x, y, z)= (13, 18, 31). If t= 1, (x, y, z)= (-2+ 13, -22+ 18, 17+ 31)= (11, -4, 48).
 

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