Finding the two radiuses that make up an ellipse

[Anonymous]

I'm sure there is a simple solution to this and as a novice user, I'm just not aware of it.  We are a custom woodshop.  I use AutoCad LT for 2D shop drawings. I have some elliptical molding to make and can generate the ellipse with the CAD, but unlike drawing a circle, double clicking on it and seeing a drop down that tells me the radius of what I've drawn, when I click on the ellipse all I get are the major and minor axis.  I have that info - I'm the one who told the machine what the major and minor axis's are.  What I need to know are the radiuses of the two circle that make up the ellipse.  I cannot make the moulding I need to make as an actual ellipse, I have to make it as two separate circles and join them together in the field to complete the ellipse (door casing).  Is there any way for the machine to tell me those two radiuses once I've created the ellipse using the ellipse tool?

Ed. Williams

Dallas, Texas

[steven-g · Accepted solution]

An ellipse isn't made up of 2 radii, which is why you cannot find that. Try changing the variable 'PELLIPSE=1' this will then draw a polyline when you use the ellipse command, the polyline will be made up of a number of arcs to give an approximation of an ellipse and you can read the radii from those arcs. Once you have that you can try yourself to reduce those arcs down to just 4 (2 large and 2 small) and see how it looks.

This site gives some other options converting-ellipses-to-arcs 

[Anonymous]

Thanks Steven,

As carpenters (not mathematicians), were were always told that an ellipse was the combination of two circles.  After having fooled around with it for an uncomfortable amount of time yesterday on the CAD, you have verified my suspicion that it is not.   

Thanks for the work-around tip.  That helps a lot.

Regards,

Ed. Williams