Date: Jul 28, 2011 1:48 AM
Author: Rob Johnson
Subject: Re: Inverse of a conic with regard to the centre is an oval of Cassini

In article <ken.pledger-E49EBA.16523828072011@news.eternal-september.org>,
Ken Pledger <ken.pledger@vuw.ac.nz> wrote:
>In article <20110727.164137@whim.org>, Rob Johnson <rob@trash.whim.org>
>wrote:
>

>> ....
>> If we invert the points (x -> x/r^2, y -> y/r^2) ....

>
>
>Then I rushed into writing

>>
>> x -> (r^2)/x, y -> (r^2)/y ?

>
>
>
>Wrong. Of course he intended r^2 = x^2 + y^2. Sorry.


I'm sorry. This post did not have a References header so it was not
linked to the original thread in my newsreader. I replied in the
original thread before I saw this post.

Rob Johnson <rob@trash.whim.org>
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