Elliptic Integrals: Arc Length of Ellipses and Elliptic Curves

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Discussion Overview

The discussion centers on elliptic integrals, specifically their relation to the arc length of ellipses and elliptic curves. Participants explore the historical context of elliptic integrals and their mathematical implications, including comparisons between ellipses and elliptic curves.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether there is an easier way to find the arc length of an ellipse, suggesting a potential misunderstanding of the relationship between elliptic integrals and elliptic curves.
  • Another participant asserts that an ellipse is indeed a type of elliptic curve, which complicates the initial claim.
  • Some participants clarify that elliptic integrals originated from the problem of determining the arc length of an ellipse, emphasizing that this is not straightforward and cannot be expressed in a simple formula.
  • There is a mention of elliptic functions being the inverse of elliptic integrals, with a specific integral formula provided as an example.

Areas of Agreement / Disagreement

Participants express disagreement regarding the simplicity of finding the arc length of an ellipse, with some asserting that it is complex while others suggest there may be simpler methods. The relationship between elliptic curves and ellipses is also contested, indicating multiple competing views.

Contextual Notes

The discussion highlights the complexity of elliptic integrals and their applications, noting that the area of an ellipse is straightforward while its circumference is not. There are unresolved assumptions regarding the definitions and distinctions between elliptic curves and elliptic functions.

amcavoy
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Taken from http://en.wikipedia.org/wiki/Elliptic_integral:

In integral calculus, elliptic integrals originally arose in connection with the problem of giving the arc length of an ellipse and were first studied by Fagnano and Leonhard Euler.

Is it just me, or does it seem like there is an easier way to find the arc length of an ellipse? I thought elliptic integrals arose in giving the arc length of elliptic curves, which as far as I know are a lot different than ellipses.
 
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I thought elliptic integrals arose in giving the arc length of elliptic curves, which as far as I know are a lot different than ellipses.

But an ellipse is an elliptic curve! :)
 
I suspect apmcavoy was thinking of "elliptic functions", as in number theory, which are quite different. In any case, he is wrong. Elliptic integrals did, indeed, arise from trying to find the arc length of an ellipse which is NOT as simple as he seems to think. The arclength of an ellipse cannot be written in any simple formula.

(The area is very simple. The area of the ellipse [itex]\frac{x^2}{a^2}+ \frac{y^2}{b^2}= 1[/itex] is just [itex]\pi ab[/itex]. The distance around (circumference?) an ellipse is not.)
 
HallsofIvy said:
I suspect apmcavoy was thinking of "elliptic functions", as in number theory, which are quite different. In any case, he is wrong. Elliptic integrals did, indeed, arise from trying to find the arc length of an ellipse which is NOT as simple as he seems to think. The arclength of an ellipse cannot be written in any simple formula.

(The area is very simple. The area of the ellipse [itex]\frac{x^2}{a^2}+ \frac{y^2}{b^2}= 1[/itex] is just [itex]\pi ab[/itex]. The distance around (circumference?) an ellipse is not.)


Elliptic functions are the inverse functions to elliptic integrals.

[tex]sn^{-1}(x) = \int^x_0 \frac{dt}{\sqrt{(1-t^2)}\sqrt{(1-k^2t^2)}}[/tex], etc.
 

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