Differential equation of all the conics in the plane

Click For Summary

Discussion Overview

The discussion revolves around the differential equation of conics in the plane, specifically focusing on the condition of having the origin as the center. Participants explore the implications of this condition and seek clarification on how it affects the general equation of conics.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants question whether setting x and y to zero in the conic equation Ax^2 + Bxy + cy^2 + Dx + ey + F is the correct interpretation of having the origin as the center.
  • Others raise the issue of defining the center of a parabola, suggesting that it may not have a natural center like other conics.
  • A participant proposes that having the origin as the center should lead to an equation with fewer parameters, although they express uncertainty about how this applies to parabolas and degenerate cases.
  • There is a repeated inquiry about what it means for the equation of the conic to have the origin as the center, with suggestions that it involves setting the equation to zero.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the definition of the center for different types of conics, particularly parabolas. There is no consensus on how to interpret the condition of having the origin as the center in the context of the general conic equation.

Contextual Notes

Participants note that the general equation for a conic is not normalized, and the implications of symmetry and parameter reduction are discussed without reaching a definitive conclusion.

Who May Find This Useful

Readers interested in differential equations, conic sections, and the geometric properties of curves may find this discussion relevant.

Michii
Messages
3
Reaction score
0
Hi, the problem is parametric families:
To find Differential equation of all the conics in the plane with the origin in the center
But when you speak of center at the origin being the equation of the conics: Ax ^ 2 + Bxy + cy ^ 2 + Dx + ey + F, is it correct to take the origin by making x and y equal to 0? Or what exactly does it refer to?
 
Physics news on Phys.org
Michii said:
Hi, the problem is parametric families:
To find Differential equation of all the conics in the plane with the origin in the center
But when you speak of center at the origin being the equation of the conics: Ax ^ 2 + Bxy + cy ^ 2 + Dx + ey + F, is it correct to take the origin by making x and y equal to 0? Or what exactly does it refer to?
I'm not sure what the question means. Where is the centre of a parabola? For anything else, you could look for a point about which the curve is symmetric.
 
Sorry I was not very clear, the question is: what does it mean that the equation of the conic has the origin in the center ?, I think that it would only be to equalize to zero the equation of the conic thus: Ax ^ 2 + Bxy + cy ^ 2 + Dx + ey + F = 0, thanks
 
Michii said:
Sorry I was not very clear, the question is: what does it mean that the equation of the conic has the origin in the center ?, I think that it would only be to equalize to zero the equation of the conic thus: Ax ^ 2 + Bxy + cy ^ 2 + Dx + ey + F = 0, thanks
No, that is a completely general equation for a conic. It is not normalised in any way.
As I wrote, for most conics you could argue that the centre is the point of maximum symmetry. Making that the origin should give you an equation with fewer parameters. (How many fewer, do you think?)
But I cannot make this work for a parabola. It has no natural centre.

Edit: also does not work for the degenerate case of a single straight line.
 
Last edited:
  • Like
Likes   Reactions: Michii
Thank you very much for your help!
 
Michii said:
Thank you very much for your help!
Did you figure out the symmetry?
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 52 ·
2
Replies
52
Views
9K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 8 ·
Replies
8
Views
4K