00:01
Okay, here we have two points in 3d space.
00:03
I want to find the equation of a line through these two points in parametric and symmetric form.
00:11
So first thing, let's call this point a, this point b.
00:17
And to find line direction, work out the vector ab.
00:21
Well, ab will be ob minus oa, and ob is the vector 9 .000.
00:32
11, a line from the origin to the point b.
00:37
Minus vector oa is 12 .9 minus 13.
00:44
So this becomes minus 19, 0, and 24.
00:54
And that's my line direction.
00:58
Now, every straight line you can write in the form, r equals a plus t, times a vector c.
01:11
Where a is a point on the line and c is line direction.
01:16
For a we could choose either a or b.
01:19
Both will work.
01:20
I would choose point a.
01:23
Point a is 12, 9 minus 13.
01:26
Then the vector a here is the same thing.
01:31
That will be 12 minus 9, minus 13 as a vector.
01:38
R is x, y, z.
01:40
A general point on the line...