Proving Uniqueness of Affine Plane Containing S & Weak-Parallel to T

In summary, for the given problem of finding a unique affine plane R that contains two affine lines S and T that are not parallel and have no intersection, the existence of R can be easily shown by considering the affine spaces S and T as p+V and q+W and taking R to be p+(V+W). To prove uniqueness, it is assumed that there exists another affine plane Q that satisfies the same conditions, but it is shown that Q and R must contain the same direction W since V does not contain W and the lines S and T are not parallel. This highlights the uniqueness of the affine plane R and the construction for existence is not repeated in the proof.
  • #1
A_B
93
1

Homework Statement


[itex]S[/itex] and [itex]T[/itex] are two affine lines in [itex]\mathbb{A}^3[/itex] that are not parallel and [itex]S\cap T=\emptyset[/itex].

Show there is a unique affine plane [itex]R[/itex] that contains [itex]S[/itex] and is weak parallel with [itex]T[/itex].

The Attempt at a Solution


Existence is easy, if [itex]S=p+V[/itex] and [itex]T=q+W[/itex] then [itex]R=p+(V+W)[/itex] satisfies the conditions.

To prove uniqueness I assume planes [itex]R[/itex] and [itex]Q[/itex] both satisfy all conditions. They both contain [itex]S[/itex] so they can be written as [itex]p+(V+vectorspace)[/itex]. That vectorspace must be [itex]W[/itex] since the planes must be weak parallel with [itex]T[/itex]so both [itex]R[/itex] and [itex]Q[/itex] are equal to [itex]p+(V+W)[/itex].

Is this good?
If it is, it still seems very ugly to me, is there a better way to do it?

Thanks
Alex
 
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  • #2
What is ugly about the solution?? It seems nice...

There is a little detail missing though. For uniqueness, you must use somewhere that S and T are not parallel.
 
  • #3
Thanks micromass!

Ok,The direction of R and Q must contain W, since V does not contain W, and is not a subspace of W (S and T are not parrallel and have dimensions 1) , "vectorspace" must be W
good now?

I feel it's ugly because it largely repeats the construction for existence.

thanks again.
 
  • #4
A_B said:
Thanks micromass!

Ok,The direction of R and Q must contain W, since V does not contain W, and is not a subspace of W (S and T are not parrallel and have dimensions 1) , "vectorspace" must be W
good now?

That's better.

I feel it's ugly because it largely repeats the construction for existence.

That's exactly why I think it's a pretty argument :smile:
 

1. How can we prove the uniqueness of an affine plane containing point S and weak-parallel to T?

The uniqueness of an affine plane containing point S and weak-parallel to T can be proven by using the axioms of affine geometry. These axioms define the properties of points, lines, and parallel lines in an affine plane. By applying these axioms, we can show that there can only be one affine plane containing point S and weak-parallel to T.

2. What are the necessary conditions for an affine plane to contain point S and be weak-parallel to T?

An affine plane must satisfy two conditions in order to contain point S and be weak-parallel to T. First, it must contain point S. Second, any line passing through point S must be parallel to line T. If these two conditions are met, then the affine plane is unique.

3. Can we use the same method to prove the uniqueness of an affine plane containing point S and strong-parallel to T?

No, the method used to prove the uniqueness of an affine plane containing point S and weak-parallel to T may not work for strong-parallel lines. Strong-parallel lines have additional properties, such as intersecting at a point at infinity, which require different axioms to prove uniqueness.

4. Is it possible for an affine plane to contain more than one point S and be weak-parallel to T?

No, an affine plane can only contain one point S and be weak-parallel to T. This is because the axioms of affine geometry state that there can only be one point on a line parallel to another line. Therefore, if an affine plane contains more than one point S, it cannot be weak-parallel to T.

5. Why is proving the uniqueness of an affine plane containing point S and weak-parallel to T important in mathematics?

Proving the uniqueness of an affine plane containing point S and weak-parallel to T is important in mathematics because it helps us understand the properties of affine geometry. Affine geometry is a fundamental concept in mathematics and is used in many fields, such as computer graphics and physics. By understanding the uniqueness of an affine plane, we can make accurate and precise calculations and models in these fields.

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