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Topic: 2 sided polygon on a sphere
Replies: 17   Last Post: Mar 14, 2008 4:54 PM

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 David W. Cantrell Posts: 3,395 Registered: 12/3/04
Re: 2 sided polygon on a sphere
Posted: Oct 5, 2004 9:00 AM

Pat_Ballew@eu.odedodea.edu ("Ballew, Pat") wrote:
> Art Mabbot wrote...
> "I thought that it was a bigon...."
> -----
> Come on Art, I've told you before, you have to let bigons be gone

Despite the nice old "Let bigons be bigons." pun, the proper term is digon.
By the way, in the plane, digons are always degenerate, of course. But on a
sphere, they need not be so.

As to the original question, although I've never heard "lune" used to
describe a shape on a sphere, that doesn't mean it's improper to do so.
But then it would seem to me that a lune on a sphere might be more general
than a digon, in that a lune could have sides which are arcs of circles
which are not necessarily great.

David Cantrell

> -----Original Message-----
> From: Art Mabbott [mailto://art@mabbott.org]
> Sent: Tuesday, October 05, 2004 7:26 AM
> To: Ballew, Pat; Mary Krimmel; John
> Cc: geometry-puzzles@mathforum.org
> Subject: Re: 2 sided polygon on a sphere
>
> I thought that it was a bigon....
>
> On 10/4/04 11:05 PM, "Ballew, Pat" <Pat_Ballew@eu.odedodea.edu> wrote:
>

> > Mary Krimmel wrote, "Is a figure on the surface of a sphere properly
> > called a polygon?"
> > -------------------
> > It is at least according to this definition from
> > http://mathworld.wolfram.com/SphericalPolygon.html
> >
> > "A closed geometric figure on the surface of a sphere which is formed
> > by the arcs of great circles. The spherical polygon is a
> > generalization of the spherical triangle.
> >
> >
> > Pat Ballew
> > Lakenheath, UK
> >
> > MathWords http://www.pballew.net/etyindex.html
> >
> >
> > -----Original Message-----
> > From: owner-geometry-puzzles@mathforum.org
> > [mailto://owner-geometry-puzzles@mathforum.org] On Behalf Of Mary
> > Krimmel
> > Sent: Tuesday, October 05, 2004 6:49 AM
> > To: John
> > Cc: geometry-puzzles@mathforum.org
> > Subject: Re: 2 sided polygon on a sphere
> >
> > At 05:51 PM 10/4/04 -0400, you [John] wrote:

> >> What is the name of a 2 sided polygon on a sphere?
> >> It rhymes with moon

> >
> > I can't tell whether this is a puzzle for the list to enjoy puzzling
> > over, or whether it's something you want answered. I doubt that I'm
> > spoiling anyone's fun by suggesting that the answer is "lune".
> >
> > Is a figure on the surface of a sphere properly called a polygon? I
> > don't know the answer, but would like to. Anyone?

Date Subject Author
10/4/04 John
10/5/04 Mary Krimmel
10/5/04 Ben Saucer
10/5/04 Pat ballew
10/5/04 Art Mabbott
10/5/04 Mary Krimmel
10/5/04 Pat ballew
10/5/04 David W. Cantrell