Determinants and Standard Orientation

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Discussion Overview

The discussion revolves around the relationship between the orientation of the rows of a matrix and the sign of its determinant, specifically in the context of standard orientation in \( \mathbb{R}^n \). Participants explore definitions of orientation and how they relate to the determinant's sign.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant inquires how to demonstrate that the sign of the determinant of a matrix \( A \) is dependent on the orientation of its rows relative to the standard orientation of \( \mathbb{R}^n \.
  • Another participant suggests that the relationship between the rows of \( A \) and the standard basis orientation is essentially the definition of orientation, prompting a request for clarification on the definition being used.
  • A third participant reiterates the previous point and provides an example involving a matrix with a positive orientation, asserting that the determinant's sign is positive due to a counterclockwise direction aligning with the standard orientation in \( \mathbb{R}^2 \.
  • One participant challenges the adequacy of a visual representation (arrows) as a mathematical definition, asking for a formal definition of orientation in the context of bases in \( \mathbb{R}^2 \.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of orientation, with no consensus reached on a formal definition or the relationship between orientation and the determinant's sign.

Contextual Notes

There is a lack of clarity regarding the definitions of orientation being referenced, and the discussion includes unresolved questions about the mathematical formalism needed to support claims made.

jakey
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How do we show that, given a matrix $A$, the sign of the determinant is positive or negative depending on the orientation of the rows of A, with respect to the standard orientation of $R^n$?
 
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Isn't that the very definition of "the rows making up the columns of A have the same (res. the opposite) orientation as the standard basis" ?

If not, write the definition of orientation. you're using.
 
quasar987 said:
Isn't that the very definition of "the rows making up the columns of A have the same (res. the opposite) orientation as the standard basis" ?

If not, write the definition of orientation. you're using.

If you refer to the attached file, this matix has a positive orientation (and the sign of the determinant is positive) since the direction from (a,b) to (c,d) is counterclockwise, which is the same orientation as R2 (counterclockwise). Thanks!
 

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I was asking that you write out the definition of what it means for a basis of R^2 to have the same (resp. the opposite) orientation as another basis of R^2.

Your little drawing with arrows does not constitute a mathematical definition.
 

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