Rotating Coordinates: Solving for x and y

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    Coordinates Rotating
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Discussion Overview

The discussion revolves around the transformation of coordinates on a curved surface, specifically focusing on the effects of rotating a tangent plane and how different equations for rotation might yield different results for the coordinates x' and y'. The scope includes mathematical reasoning and conceptual clarification regarding coordinate transformations.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant presents two equations for rotating coordinates: x' = x cos(theta) - y sin(theta) and y' = x sin(theta) + y cos(theta), questioning how the results would differ if an alternative set of equations is used.
  • Another participant seeks clarification on how changing the equations could lead to the same answer, indicating a potential misunderstanding of the transformations involved.
  • A third participant reiterates the need for clarification and refers to a diagram to illustrate the coordinate transformations, suggesting that visual representation may aid in understanding which coordinates to use.
  • Further inquiry is made about the visual representation of the points (x, y), (x', y'), and the angle theta in the context of the provided diagram.

Areas of Agreement / Disagreement

Participants express confusion and seek clarification, indicating that there is no consensus on the implications of using different equations for coordinate transformation. The discussion remains unresolved regarding the effects of these transformations.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the coordinate transformations and how they visually relate to the tangent plane on a curved surface. The dependence on the specific equations used and their interpretations is also noted.

Nusc
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If one rotates a tangent plane on a curved surface, this point can be expressed as follows:

x' = x cos(theta) - y sin(theta)
y' = x sin(theta) + y cos(theta)

One solves for x and y and computes based on the deviation of the deviation.

My question is: would the answer differ if you choose a different point say:

x' = x cos(theta) + y sin(theta)
y' = - x sin(theta) + y cos(theta)

note the negative sign.
 
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Can you please explain your question some more? How could the answer NOT change if you change the equations and the resulting values?
 
FactChecker said:
Can you please explain your question some more? How could the answer NOT change if you change the equations and the resulting values?
In the attached drawing, I can could approach this new point as

x' = x cos(theta) - y sin(theta)
y' = x sin(theta) + y cos(theta)

or

x' = x cos(theta) + y sin(theta)
y' = - x sin(theta) + y cos(theta)

From what you see in the diagram, how would you justify which coordinates?
 

Attachments

  • tangentplane.jpg
    tangentplane.jpg
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If you cannot, then what should the second pair of coordinates look like visually?
 
I still don't understand. In the diagram you posted, where are the points (x,y), (x',y'), and the angle theta?
 

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