How to Draw Lines Tangent to an Ellipse

[dswinty]

Thanks, I need every bit of help I can get.

[CarlB]

You can draw line segments tangent to an ellipse, you just need to start the line segment outside the ellipse, then use the "tan" osnap. To get the line to be a particular length, use the "lengthen" command. (Just throwing that out there, not sure what your constraints are).

[eldon]

I think you are misnaming the line you want to draw. I think it should be a chord of 2ft. The way to set these out is to draw a series of circles of radius 2ft and where the circle intersects the ellipse is your next circle centre point.

[Strix]

I'm with eldon here

sometimes it's the old drawing board methods that work best

technically an elipse has two centres, so trying to use the dead centre of one to carry out geometrical gymnastics is likely to produce skewed results

I've tried working with elipses before and remember them refusing to respond to some of the snaps and having to resort to a long hand method (perhaps using 'perpendicular' instead of tangent)

Start your circles with the first centre on the 12 o'clock point, making the centre of the next where the intersection of the first and the elipse is, and the radius equal to the length of line you need

if you need a line and not a point at the 12 o'clock position, make the first circle diameter equal to the length you need, then following circles twice the size

[dswinty]

Thanks again for all the help. I will keep working on this. Thank God this does not come up very often, but interesting problem. Will try to get it right.

[Lee Mac]

Good Luck dSwinty

Let us know how it goes

Cheers

Lee

[ibrahimgunal]

Hey guys,
I have another question related with this subjects;
I need to draw a tangent line through an arbitrary point of an ellips. I need this because after that I will draw a normal to the tangent line in contact point. Without a tangent line I can't draw a normal in autocad. I know it is not directly related with cad drawing and very complex question. But I hope there is someone who tried it before and knows a practical approximate solution..

[rkent]

First place the door, then trim from the left door jamb to the quadrant at 9 oclock so you are left with the upper left quadrant of the ellipse. Now use the divide command for however many segments you want, draw between the nodes, go from there. Depending on what you are trying to do you may want to use a complete quadrant, divide, then fit in the door and use a spacer from the window to the door, etc.

[rkent]

Hey guys,
I have another question related with this subjects;
I need to draw a tangent line through an arbitrary point of an ellips. I need this because after that I will draw a normal to the tangent line in contact point. Without a tangent line I can't draw a normal in autocad. I know it is not directly related with cad drawing and very complex question. But I hope there is someone who tried it before and knows a practical approximate solution..

Always start another thread otherwise your question will get lost in the static.