How to Determine Ellipse Axes from Cone Geometry?

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    Cone Ellipse
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Discussion Overview

The discussion centers on determining the axes of an ellipse formed by the intersection of a cone and a plane. Participants explore geometric methods to find the lengths of the major and minor axes, denoted as 'a' and 'b', without relying on quadratic equations.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant suggests that the inclination of the cutting plane provides the ratio of the axes 'a' and 'b', while the distance from the vertex of the cone gives the value of 'a'.
  • Another participant proposes a trigonometric approach to determine the axes based on the geometry of the cone and the cutting plane.
  • A later reply indicates that the distance from the vertex along the cone's axis and the cone's slope can determine the semi-minor axis, while the inclination of the plane and that distance can determine the semi-major axis.

Areas of Agreement / Disagreement

Participants present various methods and perspectives on how to derive the axes, but no consensus is reached on a singular approach or solution.

Contextual Notes

Participants do not specify the assumptions regarding the cone's dimensions or the precise nature of the cutting plane, which may affect the proposed methods.

femas
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Hi,

If the cone is cut with a plane such that an ellipse has been formed. Let's say the major axis is 'a' and the minor axis is 'b'.

Is there a way to find a and b from the geometry instead of getting them from the quadratic equation.
 
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The inclination of the plane would give the ratio a:b & its distance from the vertex of the cone would give a. I would prefer to do this trigonometrically.
 
Thank you ... But can you give me an example.
 
The distance of the plane from the vertex of the cone as measured along the axis of the cone and the slope of the cone determines the semi-minor axis of the ellipse, while the inclination of the plane together with that distance determines the semi-major axis.
 

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