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Topic: Inverse of a conic with regard to the centre is an oval of Cassini
Replies: 6   Last Post: Jul 28, 2011 7:33 AM

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Rob Johnson

Posts: 1,771
Registered: 12/6/04
Re: Inverse of a conic with regard to the centre is an oval of Cassini
Posted: Jul 28, 2011 1:48 AM
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In article <>,
Ken Pledger <> wrote:
>In article <>, Rob Johnson <>

>> ....
>> 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 <>
take out the trash before replying
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