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Topic: Collinear
Replies: 9   Last Post: May 8, 2013 1:12 PM

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 David C. Ullrich Posts: 3,555 Registered: 12/13/04
Re: Collinear
Posted: May 8, 2013 1:12 PM

On Tue, 07 May 2013 09:05:38 -0700, Barry Schwarz <schwarzb@dqel.com>
wrote:

>On 07/05/2013 08:48, William Elliot wrote:
>> Let C be a collection of n points with the property that
>> any line L with two points of C on it, has a third point
>> of C on it.
>>
>> How is it that C is collinear, ie all points of C are
>> on a single line?

>
>The assertion is not true if points are allowed to be coincident.

But the way the language is used in this sort of context,
"n points" _means_ n distinct points.

Really. You could give the same objection to
"two points determine a line"...

>For
>example
> P1 = (0,0)
> P2 = (1,0)
> P3 = (2,0)
> P4 = P5 = P6 =(1,1)
>
>

Date Subject Author
5/7/13 William Elliot
5/7/13 David Bernier
5/7/13 William Elliot
5/7/13 David Bernier
5/7/13 LudovicoVan
5/7/13 Robin Chapman
5/7/13 Barry Schwarz
5/8/13 David C. Ullrich
5/7/13 fom
5/7/13 fom