Finding Points of Intersection and Proving Parallelism with Vectors

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Discussion Overview

The discussion revolves around finding points of intersection of a line with coordinate planes and proving the parallelism of line segments in a triangle using vector concepts. It includes both theoretical and applied aspects of vector mathematics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks guidance on finding the intersection of the line defined by the parametric equations with the coordinate plane.
  • Another participant shares a proof related to the parallelism of line segments in a triangle, questioning its rigor.
  • A participant later identifies that the intersection with the XY plane occurs when z=0, calculating the corresponding t value and resulting intersection point.
  • Discussion on vector addition is presented, with participants exploring how to express the relationship between vectors a, b, and c, and their directions.
  • Clarifications arise regarding the definitions of vector addition and directionality, with participants debating the correct expressions for vector relationships.
  • One participant expresses satisfaction in understanding the vector relationships after some guidance from others.

Areas of Agreement / Disagreement

Participants generally agree on the method for finding the intersection point, but there is some disagreement regarding the definitions and relationships of the vectors involved in the proof of parallelism.

Contextual Notes

Some assumptions about the definitions of vector directions and the nature of the coordinate planes are not fully articulated, leading to potential ambiguity in the discussion.

Who May Find This Useful

Students and enthusiasts of mathematics, particularly those interested in vector calculus and geometry, may find this discussion beneficial.

StonedPanda
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How would I find the points of intersection of the line x= 3+2t , y= 7+8t , z=-2+t , that is, l(t) = (3+2t,7+8t,-2+t) with the coordinate plane?

Also, how would I prove using vectors that the line segment joining the mdpoints of two sides of a triangle is parallel to and has half the length of the third side? I'm going to try this one some more before I look for the answers, but please give me some guidance for both of them!
 
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Figured it out!

If z=0, then you have the XY plane. So, find what T value makes z zero (2 in this case).
Then, plug in 2 for t in x and y (you get 9 and 23 respectively). Thus, the point it intersects the XY plane is (9,23,0).

That feels good!
 
Make it so that a points upwards and right, make b point down and right, and make c = a + b. You know the line segment joining the midpoints is:
(1/2)a + (1/2)b
= (1/2)(a + b)
= (1/2)(c)... Q.E.D.

For the first one, I'm not sure what you're referring to by "the co-ordinate plane," but you seem to have gotten that one, so you're fine.
 
Scuse me akg! It should have been Coordinate Planes =p mb

But, wouldn't c = a - b if a points upright and b points downright?
 
Not if you define c as a + b!

cookiemonster
 
StonedPanda said:
Scuse me akg! It should have been Coordinate Planes =p mb

But, wouldn't c = a - b if a points upright and b points downright?
Nope, it would be as I wrote it. Think about it: start at the "starting point" of a, and go in the direction that it goes in. Now, since you're adding b, you then proceed in the direction that b goes in, which is down. In this process you will have started at the "start" of c and ended at the "end."
 
Ok, I get it. If a points downleft and b points downright, then c is b-a . Is this correct sir?

Btw, thanks for your help akg and cook!
 
Yes, that's correct.
 
  • #10
Vectors are incredibly powerful. I've taken 4 classes of multivarient calc so far, and my knowledge of math increased exponentially!
 

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