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Topic: cotpi 69 - Black and white plane
Replies: 26   Last Post: Oct 9, 2013 10:23 AM

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Mike Terry

Posts: 662
Registered: 12/6/04
Re: cotpi 69 - Black and white plane
Posted: Oct 2, 2013 10:29 PM
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"quasi" <quasi@null.set> wrote in message
news:v9vo49lvr7j4ns7i82s869ou749lgdmrup@4ax.com...
> Pubkeybreaker wrote:
> >Susam Pal wrote:
> >>
> >> How can you construct a plane where every point is coloured
> >> either black or white such that two points of the same colour
> >> are never a unit distance apart?
> >>
> >> -- Originally posted at:
> >> http://cotpi.com/p/69/
> >> Puzzles IRC channel:
> >> ##puzzles on irc.freenode.net
> >> Puzzles IRC webchat:
> >> http://webchat.freenode.net/?channels=##puzzles

> >
> >It does not seem possible. Take any point. Suppose it is
> >white. It is the center of a circle (of radius 1). All points
> >on that circle must then be black. But given any point on
> >that circle there is another point on the circle at distance 1.
> >Both points are the same color.
> >
> >Unless, of course, I am being completely stupid.

>
> No, your proof is fine.
>
> quasi


The question was asked here a few years ago whether the plane can be
coloured along the lines above but using three colours. The answer is no,
and the proof is similar but less obvious...

Regards,
Mike.





Date Subject Author
10/2/13
Read cotpi 69 - Black and white plane
cotpi
10/2/13
Read Re: cotpi 69 - Black and white plane
Pubkeybreaker
10/2/13
Read Re: cotpi 69 - Black and white plane
quasi
10/2/13
Read Re: cotpi 69 - Black and white plane
Mike Terry
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/6/13
Read Re: cotpi 69 - Black and white plane
quasi
10/6/13
Read Re: cotpi 69 - Black and white plane
quasi
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/6/13
Read Re: cotpi 69 - Black and white plane
quasi
10/6/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/9/13
Read Re: cotpi 69 - Black and white plane
Phil Carmody
10/9/13
Read Re: cotpi 69 - Black and white plane
David Bernier
10/2/13
Read Re: cotpi 69 - Black and white plane
Eric Lafontaine
10/2/13
Read Re: cotpi 69 - Black and white plane
Michael F. Stemper
10/2/13
Read Re: cotpi 69 - Black and white plane
quasi
10/2/13
Read Re: cotpi 69 - Black and white plane
quasi
10/2/13
Read Re: cotpi 69 - Black and white plane
Haran Pilpel
10/2/13
Read Re: cotpi 69 - Black and white plane
quasi
10/2/13
Read Re: cotpi 69 - Black and white plane
quasi
10/2/13
Read Re: cotpi 69 - Black and white plane
Ted Schuerzinger
10/2/13
Read Re: cotpi 69 - Black and white plane
Mark Brader
10/3/13
Read Re: cotpi 69 - Black and white plane
William Elliot

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