Perpendicular Lines in Three Space

In summary, the conversation discusses finding the equation of a line L2 that is perpendicular to a given line L1 and passes through a specific point, with a given direction vector. The solution involves finding a vector that is perpendicular to the direction vector of L1 and using it to determine the equation of L2. There may be multiple solutions, but any of them would work.
  • #1
dogma
35
0
Hello,

Please bear with me...my brain is in vapor lock.

I have a line L1 given by the following parametric equations:

x = 2+3t, y = -1+5t, z = 8+2t

I need to find the equation of a line L2 passing through point B = (1,2,5) and perpendicular to L1.

For the life of my tired, worn out brain...I cannot figure out how to determine the direction numbers that would make L2 perpendicular to L1 (with direction numbers (3,5,2)).

Can someone please give my brain a kick start.

Thanks a bunch.

dogma
 
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  • #2
Any vector [itex](x, y, z)[/itex] such that [itex](3, 5, 2) \circ (x, y, z) = 0[/itex] has direction perpendicular to that of your line.
 
Last edited:
  • #3
That makes sense, but I can see a couple of soulutions to that:

(a,b,c) = (1,-1,1), (-1,1,-1),(1,-3,6),...

If I'm on the right track, how do I determine which is correct?

Thanks again.
 
  • #4
dogma said:
That makes sense, but I can see a couple of soulutions to that:

(a,b,c) = (1,-1,1), (-1,1,-1),(1,-3,6),...

If I'm on the right track, how do I determine which is correct?

Thanks again.

Any of those would work. Pick one and figure out the intercepts.
 
  • #5
okay, my brain is starting to show some activity...thanks all

dogma
 

1. What are perpendicular lines in three space?

Perpendicular lines in three space are lines that are at right angles to each other and intersect at a single point. They are also known as orthogonal lines.

2. How do you determine if two lines are perpendicular in three space?

To determine if two lines are perpendicular in three space, you can use the dot product of their direction vectors. If the dot product is equal to zero, then the lines are perpendicular. Another method is to calculate the angle between the two lines using the dot product and if the angle is 90 degrees, then the lines are perpendicular.

3. Can two lines be perpendicular in three space if they are not in the same plane?

No, two lines cannot be perpendicular in three space if they are not in the same plane. Perpendicular lines must intersect at a single point, so they must lie on the same plane.

4. Are perpendicular lines in three space always at right angles to each other?

Yes, perpendicular lines in three space are always at right angles to each other. This is because they are defined as lines that intersect at a right angle.

5. How are perpendicular lines in three space used in real life?

Perpendicular lines in three space are used in various fields such as engineering, architecture, and physics. They are used to determine the shortest distance between two points, to construct right angles, and to analyze the motion of objects in space.

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