A circle tranforming into ellipse

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SUMMARY

The discussion focuses on the geometric transformation of a circle into an ellipse through orthogonal projection onto inclined planes. The relationship between the angle of inclination (θ) and the eccentricity of the resulting ellipse is established, where the semi-major axis (a) equals the radius (r) of the circle, and the semi-minor axis (b) is defined as b = rcosθ. The user seeks a mathematical proof demonstrating that the inclined projection of a circle results in an ellipse, emphasizing the concept of non-uniform scaling as a key factor in this transformation.

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  • Understanding of geometric projections
  • Familiarity with the properties of ellipses
  • Knowledge of trigonometric functions, specifically cosine
  • Basic concepts of non-uniform scaling in geometry
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  • Explore geometric transformations, particularly non-uniform scaling
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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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