# Thread: Parametric equations

1. ## 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??)

2. 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

3. 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 :

But :

THE Parametric equations IS :

4. 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?

5. 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)