an ellipse problem

T

Tonyaimer

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Apr 28, 2024
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I am trying to fit a curve for the nose of a scale model aeroplane.

The nose contour takes the form of an ellipse ( ellipsoid in 3D ) and I know the minor semi axis and one point on the minor axis which establishes this minor
semi axis and the ellipse is tangent to the horizontal at this point.

I do not know the major semi axis or the focii of the ellipse.

I am hoping that knowing two points on the ellipse ( including the one above "b" ) will enable me to establish the "a" value.

My version of AutoCAD ( R10 ) approximates an ellipse with arcs and this is causing me problems.

I am obviously only trying to establish the equation for one quarter of the full ellipse.

Is this possible with these two points of will I need more points?

Tony
 
Tonyaimer said:
I am trying to fit a curve for the nose of a scale model aeroplane.

The nose contour takes the form of an ellipse ( ellipsoid in 3D ) and I know the minor semi axis and one point on the minor axis which establishes this minor
semi axis and the ellipse is tangent to the horizontal at this point.

I do not know the major semi axis or the focii of the ellipse.

I am hoping that knowing two points on the ellipse ( including the one above "b" ) will enable me to establish the "a" value.

My version of AutoCAD ( R10 ) approximates an ellipse with arcs and this is causing me problems.

I am obviously only trying to establish the equation for one quarter of the full ellipse.

Is this possible with these two points of will I need more points?

Tony
Click to expand...
Just a quick response to bring your question back "in play". 👍😊
(See here.)
 
Tonyaimer said:
I am trying to fit a curve for the nose of a scale model aeroplane.

The nose contour takes the form of an ellipse ( ellipsoid in 3D ) and I know the minor semi axis and one point on the minor axis which establishes this minor
semi axis and the ellipse is tangent to the horizontal at this point.

I do not know the major semi axis or the focii of the ellipse.

I am hoping that knowing two points on the ellipse ( including the one above "b" ) will enable me to establish the "a" value.

My version of AutoCAD ( R10 ) approximates an ellipse with arcs and this is causing me problems.

I am obviously only trying to establish the equation for one quarter of the full ellipse.

Is this possible with these two points of will I need more points?

Tony
Click to expand...
Please sketch the curve and the facts you know, so we can have a better idea what is known and what is not. Actual measurements would be even better.
 
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