Vector equation of a spherical curve

Click For Summary

Discussion Overview

The discussion revolves around the parametric representation of a curve defined by the function r(t) = (cos^2(t), sin(t), sin(t)*cos(t)) and whether this curve describes a spherical shape. Participants explore the relationship between the curve and the equation of a sphere, considering both theoretical and mathematical aspects.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asks how to prove that the given curve describes a spherical shape and expresses uncertainty about reconciling the parametric representation with the expression of a sphere.
  • Another participant suggests using the equation x^2 + y^2 + z^2 = r^2, presuming r = 1, and recommends plugging in the values for x, y, and z while applying trigonometric identities.
  • A later reply indicates that the curve may lie on the surface of a sphere but questions whether it can be considered a sphere itself, referencing the axiom of choice in relation to space-filling curves.
  • One participant acknowledges the assumption of a unit sphere centered at the origin, suggesting that this simplifies the understanding of the curve's relationship to a spherical surface.
  • Another participant counters the claim about the necessity of the axiom of choice for constructing space-filling curves, providing a reference to an external source for further exploration.

Areas of Agreement / Disagreement

Participants express differing views on whether the curve can be classified as a sphere or merely as lying on the surface of a sphere. There is no consensus on the implications of the axiom of choice in this context.

Contextual Notes

The discussion includes assumptions about the nature of the curve and its relationship to spherical geometry, as well as references to mathematical concepts that may not be fully resolved within the thread.

BilalX
Messages
7
Reaction score
0
Given a curve described by the following function:
r(t) = (cos^2(t), sin(t), sin(t)*cos(t)), 0 ≤ t ≤ 2*Pi

How can I prove it describes a spherical shape? I know that the parametric representation is the following, but I'm not sure how to reconcile that with the expression of a sphere.

x = cos^2(t)
y = sin(t)
z = sin(t)*cos(t)

I'd greatly appreciate any insight, thanks.
 
Physics news on Phys.org
BilalX said:
Given a curve described by the following function:
r(t) = (cos^2(t), sin(t), sin(t)*cos(t)), 0 ≤ t ≤ 2*Pi

How can I prove it describes a spherical shape? I know that the parametric representation is the following, but I'm not sure how to reconcile that with the expression of a sphere.

x = cos^2(t)
y = sin(t)
z = sin(t)*cos(t)

I'd greatly appreciate any insight, thanks.

Well, for a sphere the x^2+y^2+z^2=r^2
I presume in your case r is equal to one. Plug in the values for x, y,z above and apply trigonometric identities. That said, I don't think a curve can fill an area without appealing to the axiom of choice. Thus perhaps your curve is on the surface of a sphere but I don't think it is a sphere.
 
John Creighto said:
Well, for a sphere the x^2+y^2+z^2=r^2
I presume in your case r is equal to one. Plug in the values for x, y,z above and apply trigonometric identities. That said, I don't think a curve can fill an area without appealing to the axiom of choice. Thus perhaps your curve is on the surface of a sphere but I don't think it is a sphere.

Oh, right, I just didn't think of assuming a unit sphere centered at the origin - much easier now. And yeah, the curve just follows a spherical surface.

Thanks-
 
John Creighto said:
Well, for a sphere the x^2+y^2+z^2=r^2
I presume in your case r is equal to one. Plug in the values for x, y,z above and apply trigonometric identities. That said, I don't think a curve can fill an area without appealing to the axiom of choice. Thus perhaps your curve is on the surface of a sphere but I don't think it is a sphere.
You can construct space-filling curves without the use of Choice. For example, see the construction given at http://en.wikipedia.org/wiki/Space-filling_curve .
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 11 ·
Replies
11
Views
7K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
3
Views
5K