tangential placement of a curve on curve

[spider80]

I have to place a fillet (curved end of an object), say curve A tangent to another curve, say curve B. One constraint I have is the location of curve A is fixed from the horizontal plane. Curve B is fixed in all respects (x,y,z). So if I want to place curve A tangential to B at a particular value above the horizontal plane, how can I ensure tangency between the two curves.
Here is what I did. I fixed the vertical distance of curve B, turned on my ortho and moved the curve B horizontally very slowly and kept regenerating. When I was reasonably close I made sure I snapped to the horizontal and tangent.
What I have right now looks right, but am not sure if I am convincing myself the right way.
How do I go about this?
Thanks

 

[IFRs]

Can you use the TAN OSnap?

 

[diamondjim]

Are you saying that you want both
curves to have their maximum point
on the horizontal line? If so
you can draw a strait line strait
up from the center of each curve
at a length equal to its radius of
curvature.
Then move the intersections of the
strait line and each curve to the
horizontal position.

 

[chicopee]

So what you are saying is that curve A can have its center anywhere on an X axis parallel to your horizontal plane. Knowing the radii of both curves, sum them up and draw an arc having a radius of that summation and whose center is the center of curve B. Let that arc intersect the X axis of curve A and that intersection will be curve A center from which you can draw curve A and which will be tangent to curve B.