Re: equidistant sets

klewis@xxxxxxxxxxxxxxx (Keith A. Lewis) writes in article <dmi561$gfi$1@xxxxxxxxxxxxxxxxxxx> dated Tue, 29 Nov 2005 18:03:45 +0000 (UTC):
>quasi <quasi@xxxxxxxx> writes in article <qapno1tk69c9q2nk118vub7mpsmb2lg9ud@xxxxxxx> dated Tue, 29 Nov 2005 00:26:38 -0500:
>>Actually, it's an ellipse, not a circle.

You're right. My derivation was in error.

eqd(circle, interior point) is the set of points whose distances from the
center of the circle and from the interior point add up to the radius of the
circle. So the foci are at the center and at the interior point. It's only
a circle when the interior point and the center are equal.

>I thought that might be the case, so I worked out the equation before I
>posted. For a circle of radius r centered at (0,0) and a point at (-h,0)
>where 0<=h<r I get a solution of:

[snip incorrect solution]

--Keith Lewis klewis {at} mitre.org
The above may not (yet) represent the opinions of my employer.
.

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