Quick Qns : Convergence in Polar Coordinates

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Discussion Overview

The discussion revolves around the concept of limits in the context of polar coordinates, specifically examining whether the convergence of a function as (x,y) approaches (0,0) can be simplified to considering only the radial component (r) while disregarding the angular component (theta).

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that in polar coordinates, the statement "(x,y) tend to (0,0)" is equivalent to "r tend to 0" and questions the relevance of theta.
  • Another participant counters that theta does matter, emphasizing that the limit in R^2 exists only if it is independent of the path taken, which includes consideration of theta.
  • A third participant asserts that if the limit exists and is independent of the path, then the angle does not matter.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of theta in the limit process, indicating that the discussion remains unresolved regarding the role of the angle in determining limits in polar coordinates.

Contextual Notes

The discussion highlights the dependence on the path taken to approach the limit, suggesting that assumptions about the behavior of the function may vary based on the chosen approach.

Legendre
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Suppose we investigating the limit of a function on R^2 as (x,y) tend to (0,0).

We convert the function into polar coordinates.

Then "(x,y) tend to (0,0)" is equivalent to "r tend to 0"?

Theta (the angle) does not matter?
 
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Legendre said:
Suppose we investigating the limit of a function on R^2 as (x,y) tend to (0,0).

We convert the function into polar coordinates.

Then "(x,y) tend to (0,0)" is equivalent to "r tend to 0"?

Theta (the angle) does not matter?
Yes, the angle theta certainly matters. As no doubt you know, a limit it R2 only exists if the value of the limit is independent of the path along which the limit is taken. You would also need to account for theta if, for example, you were asked to compute the limit along a certain path.
 
But if the limit itself exists, the fact that it is independent of the path means that the angle does not matter.
 
Thanks for the input~
 

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