Hello guys, I'm kinda of stuck in this question:
"Find the simetric and parametric equation of the line that has the point (0,0,0) and is perpendicular (by intersection) to the line:
"
First, you should be able to see that the line (x- 10)/4= y/3= z/2, which is the same as the line given by parametric equations, x= 10+ 4t, y= 3t, z=2t, has direction vector <4, 3, 2>. Further, any line through (0, 0, 0) to (a, b, c) can be written as x= as, y= bs, z= cs and has direction vector <a, b, c>. If the two lines are perpendicular, then their dot product, <4, 3, 2>.<a, b, c>= 4a+ 3b+ 2c= 0. Since the two lines intersect, we can take (a, b, c) to be a line on the given line and so must satisfy the equation: (a- 10)/4= b/3= c/2. That gives two equations for a, b, and c. Since we only want the equation of the line, and not a specific point, it is sufficient to solve for either of two unknows in terms of the other one, then choose a convenient value for it.
Thanks in advance for the help HallsofIvy
But... look:
I got this equation: 4a+3b+2c = 0
And from (a- 10)/4= b/3= c/2 I get b = 3c/2
Putting b in the first equation I got: a = -13c/8; b = 3c/2; c = c
How can I advance?
x = ta so => x = -13ct/8, even if I consider c as 1 it still gets wrong,
The answer is: x = 13t y = -12t z = -8t
Guys, I'm really close to finish the question, please one last help:
Question: Find the simetric and parametric equation of the line that has the point (0,0,0) and is perpendicular (by intersection) to the line:
Attempt:
1) The line in the question has the following direction vector: <4,3,2>
2) If the line I want is perpendicular to it => <4,3,2>.<a,b,c> = 0 => 4a + 3b + 2c = 0
3) Since the two lines intersect, we can use the equation of the line in question to a point in the equation I want:
4) From the equation of the step above, I find:
5) And using the "b" above in the equation of the second step:
And now, I dont see how can I advance...
I mean, if I try: and consider c as 1 I get a wrong "a"
Please?
You know, as I said before, that any line through the origin can be written in the form x= at, y= bt, z= ct. So this line is of the form x= -(13/8)ct, y= (3/2)ct, z= ct which you can write as x= -(13/8)s, y= (3/2)s, z= s with s= ct. That is your parametric equation. Or, if you don't like fractions, take c= 8 so that x= -13t, y= 12t, z= 8t.
To write as "symmetric equations" solve each of those for t:
And now, I dont see how can I advance...
I mean, if I try: and consider c as 1 I get a wrong "a"
Please?