Are A, B, and A+B Always Coplanar?

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Discussion Overview

The discussion centers on the coplanarity of vectors, specifically whether two free vectors A and B, along with their sum A+B, are always coplanar. Participants explore the implications of linear dependence among vectors and the associated geometric interpretations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that two free vectors are always coplanar and that A, B, and A+B are coplanar as they define a plane.
  • Another participant introduces the concept of linear dependence, stating that if two vectors are linearly dependent, they are collinear and thus coplanar.
  • A participant suggests a pattern where if n vectors are linearly dependent, they are co(n-1 space object) and are always co(n space object), proposing a generalization based on dimensionality.
  • There is a discussion about terminology, with one participant questioning the existence of a specific term for three-dimensional coplanarity, while another believes "coplanar" is the appropriate term.

Areas of Agreement / Disagreement

Participants generally agree on the coplanarity of two vectors and their sum, but there is some disagreement regarding the terminology and the implications of linear dependence for three or more vectors. The discussion remains unresolved regarding the generalization of coplanarity for n vectors.

Contextual Notes

Participants express uncertainty about the terminology for higher-dimensional coplanarity and the implications of linear dependence, which may depend on specific definitions and assumptions about vector spaces.

Who May Find This Useful

Readers interested in vector mathematics, linear algebra, and geometric interpretations of vector relationships may find this discussion relevant.

1MileCrash
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Two free vectors are always coplanar.

Then if A and B are free vectors, are A, B, and A+B all coplanar in all cases?
 
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1MileCrash said:
Two free vectors are always coplanar.

Then if A and B are free vectors, are A, B, and A+B all coplanar in all cases?
Yes.
Any two vectors that start from the same point (you can assume that they start from the origin) determine a plane. Any linear combination of these vectors (including 1*A + 1*B) also lies in that same plane.
 
Cool.

How about this:

If two vectors are linearly dependent, they are collinear. They are always coplanar.

If three vectors are linearly dependent, they are coplanar. Three vectors are always all co"cubeular" (I don't know a word like coplanar for a three dimensional object.)

Based on this pattern, it correct to say that:

If n vectors are linearly dependent, then they are co(n-1 space object) and are always co(n space object).

Since for two vectors, an n-1 space object is a line, for three it is a plane, and so on.

Am I making sense?
 
Last edited:
1MileCrash said:
Cool.

How about this:

If two vectors are linearly dependent, they are collinear. They are always coplanar.
Yes. If two vectors are linearly dependent, then each is a nonzero scalar multiple of the other.
1MileCrash said:
If three vectors are linearly dependent, they are coplanar.
They could be collinear, depending on which vectors we're talking about.
1MileCrash said:
Three vectors are always all co"cubeular" (I don't know a word like coplanar for a three dimensional object.)
I don't believe there is any special terminalogy beyond coplanar.
1MileCrash said:
Based on this pattern, it correct to say that:

If n vectors are linearly dependent, then they are co(n-1 space object) and are always co(n space object).

Since for two vectors, an n-1 space object is a line, for three it is a plane, and so on.

Am I making sense?
Yes, I get what you're saying, but as I said, I don't believe there is any terminology beyond coplanar.
 

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