Sorry, I just realized that I made a stupid mistake when I derived the distance
of the center of the circle from the centers of the spheres.  I'll try to
derive the correct equation in school today and will post it if nobody else
beats me to it.

Mark Wagner wrote:

> Kevin Wampler wrote in message <3876DA06.B2A9AC10@tapestry.tucson.az.us>...
> >Mark Wagner wrote:
> >
> >> Given the centers and radii of two overlapping spheres, what is the
> equation
> >> for the circle where the two spheres intersect?  I need this for a
> project
> >> I'm working on.
> >>
> >> Mark
> >
> >What form do you need this equation in?
> >
> >If r1 and r2 are the radii of the two spheres and d is the distance between
> >their centers, then the radius of the circle of their intersection should
> be:
> >
> >sqrt(-(d+r1+r2)*(d-r1+r2)*(d+r1-r2)*(d-r1-r2))/(2*d)
> >
> >This circle will be centered on the line connecting the centers of the
> spheres
> >and will be
> >
> >(d+r1-r2)/2
> >
> >units away from the center of the first sphere and
> >
> >(d+r2-r1)/2
> >
> >units away from the center of the second sphere.  The circle will also be
> >oriented so that it is orthogonal to the line connecting the centers of the
> >spheres.
> >
> >I hope that this is helpful.
>
> Thanks!  I should be able to work with this.
>
> Mark

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