Conical Representation of Sphere

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Discussion Overview

The discussion revolves around the geometric relationship between spheres and cones, specifically whether a sphere can be considered a generalized form of a cone or vice versa. Participants explore the implications of rotating geometric shapes and the properties of hyperboloids in relation to cubes and other forms. The scope includes conceptual and mathematical reasoning.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Some participants propose that a sphere may be viewed as a more generalized form of a cone, formed by the 360° rotation of a cone.
  • Others argue that a cone could be considered a more generalized form of a sphere, as a sphere can be created by rotating a zero eccentric planar intersection of a cone about the Z axis.
  • A participant notes that a sphere is a degenerate case of an ellipsoid, similar to how a circle is a degenerate case of an ellipse.
  • There is confusion regarding the relationship between hyperboloids and cubes, with one participant questioning how a cube, a linear geometric form, can be derived from a hyperboloid, which involves three variables.
  • Another participant clarifies that a cube requires multiple equations and inequalities to represent its six faces, contrasting this with the properties of hyperboloids, which can be of one or two sheets depending on the axis of rotation of a hyperbola.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between spheres and cones, with no consensus reached. The discussion also reveals confusion and disagreement regarding the geometric properties of hyperboloids and cubes.

Contextual Notes

Participants highlight the complexity of representing geometric forms mathematically, noting the need for multiple equations and inequalities for shapes like cubes, which contrasts with the simpler representations of hyperboloids.

Leo Authersh
Is Sphere a more generalized form of Cone i.e. formed by 2 dimensional rotation to 360° of a cone?

Or is Cone a more generalized form of Sphere since sphere can be formed by rotating about Z axis a zero eccentric planar intersection of a cone?

@fresh_42 @FactChecker @WWGD
 
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Leo Authersh said:
Is Sphere a more generalized form of Cone i.e. formed by 2 dimensional rotation to 360° of a cone?

Or is Cone a more generalized form of Sphere since sphere can be formed by rotating about Z axis a zero eccentric planar intersection of a cone?

@fresh_42 @FactChecker @WWGD
A sphere is a degenerate case of an ellipsoid just as a circle is a degenerate case of an ellipse.
 
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Leo Authersh said:
But what confuses me is that, if the hyperboloid is rotated to 90°, we get a cube.
Why do you think this?
Leo Authersh said:
How is a cube which is a linear geometric form that has one variable be formed by a Hyperboloid that has three variables?
This isn't right, either. Let's look at two dimensions first. The unit square in the first quadrant does not have a single equation. Instead, it has four equations, one for each side, along with inequalities that indicate the minimum and maximum values of the variable on each side. For example, the upper horizontal side would be represented by the equation y = 1, and the inequality ##0 \le x \le 1##. There would be an equation/inequality pair for each side.

For a cube you would need equation/inequality pairs for each of the six faces.

Back to the hyperboloid. There are actually two kinds of hyperboloids -- hyperboloid of one sheet (or surface) and hyperboloid of two sheets (two distinct surfaces). If you take the hyperbola ##x^2 - y^2 = 1## and rotate it about the x-axis, you get a hyperboloid of two sheets (in three dimensions). If you rotate the same hyperbola about the y-axis, you get a hyperboloid of one sheet.

Do a web search on, say, wikipedia for hyperboloid to see the formulas and graphs of these quadric surfaces.

Mod note: Thread moved to General Mathematics -- the question isn't really about topology or analysis.
 

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