How to make an arc that follows part of an ellipse?

[Jennifer]

I want to show how two ellipses overlap by having a dotted line on the one on top follow the edge of the one on the bottom.

I tried drawing both a line and an arc across the portion of the ellipse that goes under the top ellipse and then using the pencil tool, drag the middle point out. But the radius is not quite right.

Is there a better way?

[wapperdude]

This might be of interest...uses points along path.

[RudySchneider]

This is actually a bit of work, but easily doable.  The attached file includes instructions.

[vojo]

or see the response to Jennifer's post
Just below this post