A circle tranforming into ellipse

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    Circle Ellipse
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Discussion Overview

The discussion revolves around the geometric transformation of a circle into an ellipse when projected onto an inclined plane. Participants explore the relationship between the angle of inclination and the resulting eccentricity of the ellipse, as well as seek mathematical proofs for the transformation process.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant describes a scenario involving two parallel planes where a circle is projected orthogonally onto another plane, leading to an ellipse upon inclination.
  • Another participant proposes a relationship where the semi-major axis (a) equals the radius of the circle (r) and the semi-minor axis (b) equals rcosθ, with θ representing the angle of inclination, and mentions finding the eccentricity of the ellipse.
  • A different participant suggests visualizing the projection of a circle as a cylinder, indicating that the inclined plane intersects the cylinder, which may help in understanding the transformation.
  • One participant expresses a desire for a mathematical proof that a non-uniform scaling of a circle results in an ellipse.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the mathematical proof of the transformation from a circle to an ellipse, and multiple viewpoints regarding the geometric interpretation and relationships involved remain present.

Contextual Notes

There are limitations regarding the assumptions made about the projection and inclination, as well as the definitions of the axes and eccentricity that may not be fully resolved in the discussion.

vin300
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I don't know what category this question falls into. I have two parallel planes, on one I draw a circle and on the other I project it orthogonally. Now I incline the plane with the circle. The projection on the other plane will be an ellipse. I need to find out, the relationship between the angle of inclination and the eccentricity of the ellipse.
 
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I've figured it out. If a is the semi-major axis, b is the semi-minor axis of the ellipse and r is the radius of the circle, then a= r and b= rcosθ (θ is the angle of inclination). Now it isn't difficult to find the eccentricity of the ellipse. But.. how to prove that an inclined projection of a circle is an ellipse in the first place?
 
Look at the projection of a circle between parallel planes as a cylinder. then the angle of the second plane intersects the cylinder.
 
I was looking for a mathematical proof of "a non-uniform scaling of a circle changes its shape into an ellipse".
 

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