How do i find the arc length of an implicit curve given by f[x,y]=0?

Click For Summary

Discussion Overview

The discussion revolves around finding the arc length of an implicit curve defined by the equation f[x,y]=0. Participants explore the challenges of applying the arc length formula when the curve cannot be easily parameterized, and they consider the implications of the implicit function theorem.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant used the implicit function theorem to derive dy/dx and attempted to apply the arc length formula, but encountered difficulties integrating with respect to x due to the implicit function y[x] within the radical.
  • Another participant noted that the specific function f(x,y) significantly affects the approach to finding the arc length.
  • A participant expressed disappointment at the lack of a general formula or algorithm for this problem, highlighting that the only information available is that the curve cannot be parameterized.
  • There was a challenge regarding the assertion that every curve can be represented by parametric functions, with one participant questioning whether the complexity of such representations was the issue.
  • Another participant clarified that while the complexity of parametric representations can vary, any curve defined by analytic functions can indeed be parameterized.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the ability to parameterize every implicit curve, with some asserting it is possible while others express uncertainty about the complexity involved.

Contextual Notes

The discussion highlights limitations related to the specific form of the function f[x,y] and the implications of the implicit function theorem, as well as the challenges posed by integrating with respect to x when dealing with implicit curves.

okkvlt
Messages
53
Reaction score
0
?
i used the implicit function theorem to find dy/dx, then applied that to the arc length formula, but i have to integrate with respect to x and there is the implicit function y[x] inside the radical.
also, if it matters, the curve is assumed to be closed.
 
Physics news on Phys.org
That depends strongly on what the specific function is. What is f(x,y) for this problem?
 
So there's no general formula/algorithm? bummer. there is no information about the curve other than it cannot be parameterized(and trivially, cannot be put into the form y[x]
 
I am puzzled by this. Every curve can be given some parametric functions. And every curve can be written in terms of piecewise functions. Do you mean simply that you do not know what they are or that they would be very complicated?
 
in general they would range in complexity. I am writing a program that finds the arc length of a level curve of some function f[x,y]. do you mean every implicit curve has a parametric representation?
 
I second HallsofIvy assertion that any curve (at least any curve that is implicitly or explicitly defined with analytic functions) can be parametrized.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K