# Parametric equations

• July 27th 2009, 06:38 PM
chengbin
Parametric equations
Determine the equation of line g which passes through point A(1,-1,3) and is parallel to the x-axis,

Letting $\vec u$ be the direction vector of line g,

$\vec u=(1,0,0)$ (Why??)
• July 27th 2009, 06:49 PM
songoku
Because the line g is parallel to the x-axis, the direction will be (1,0,0).
The value of the direction is on the x-direction only, leaving the others zero
• July 28th 2009, 04:15 AM
dhiab
Quote:

Originally Posted by chengbin
Determine the equation of line g which passes through point A(1,-1,3) and is parallel to the x-axis,

Letting $\vec u$ be the direction vector of line g,

$\vec u=(1,0,0)$ (Why??)

Hello Thank you This the solution :
The line is definite by :http://mathramz.com/xyz/latexrender/...edc6222471.png

But :
http://mathramz.com/xyz/latexrender/...ac5d367b00.png
THE Parametric equations IS :
http://mathramz.com/xyz/latexrender/...5ba8877fc3.png
• July 28th 2009, 04:42 AM
chengbin
Quote:

Originally Posted by songoku
Because the line g is parallel to the x-axis, the direction will be (1,0,0).
The value of the direction is on the x-direction only, leaving the others zero

Why is x=1?
• July 28th 2009, 11:46 PM
songoku
You can choose x = 2, 3, 1/3, etc..

let x = 2
$\vec u = (2,0,0) = 2 (1,0,0)$

let x = 3
$\vec u = (3,0,0) = 3 (1,0,0)$

For the direction of a vector, usually the simplest form is used which is (1,0,0)