Re: 4 spheres inside a tetrahedron

On 28 Sep 2005 21:02:31 -0700, "jmorriss@xxxxxxxxxxx"
<jmorriss@xxxxxxxxxxx> wrote:

>The only condition I can think of is that the smallest sphere not fall
>through the gap where the first three meet.

Now that you state it that way, it seems obvious. Thanks.

Ok, so the question then is this:

Given 3 mutually tangent spheres with radii r1<=r2<=r3, what is the
smallest radius r4 such that a sphere of radius r4 can be placed
mutually tangent to the other 3? In other words, find r4 such that any
sphere of radius less than r4 could fall right through without
touching (in basketball terminology -- "swish").

>Did you possibly mean 5 spheres?

No I meant 4 -- I just had a blind spot.

>See http://www.pballew.net/soddy.html

Can't seem to get that link.

quasi
.

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