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Joined: Jan 2003
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stranger
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OP
stranger
Joined: Jan 2003
Posts: 2 |
Thanks to everyone who responded. The second post by etaoin gave me a direct answer. I'm going to use pentakaidecagon but will allow that pentadecagon is also correct.
Thanks again,
John Whittier
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
Joined: Jan 2001
Posts: 13,858 |
Any geometers on the Board? I was able to repeat the construction, but as yet do not see
how to prove it. That will be something to work on while the board is quiet.I'd welcp,e some
competition.
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
Joined: Jan 2001
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The motto of Plato's Academy was:. "Let no one ignorant of geometry enter here.:
Have we no geometers here?
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Joined: Dec 2002
Posts: 122
member
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member
Joined: Dec 2002
Posts: 122 |
>I found a site to construct a regular pentagon. It is fairly short, but I haven't mastered it yet.Albrecht Durer in his book Anderweysung der messung mit der zirckel und richtscheyt in Linien ebnen und gantzen corporen durch Albrecht Durer zusamen getzogen und zu nutz aller kunstliebhabenden mit zugehorigen figuren in truck gebracht im jar MDXXV  presented very simple and elegant way how to form a regular pentagon only with a ruler and one base of a circle (hope it means what i wanted to say  ). i've read that the construction is not perfect but for practical goals - good enough.
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Joined: Mar 2000
Posts: 6,511
Carpal Tunnel
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Carpal Tunnel
Joined: Mar 2000
Posts: 6,511 |
im jarShouldn't that be "jahr"?
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
Joined: Jan 2001
Posts: 13,858 |
Shouldn't that be "jahr"?
Ja.
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
Joined: Jan 2001
Posts: 13,858 |
Here's a URL that just with compass step hy step constructs a regular pentagon. Down at bottom of the green screen the is a circle that can be moved by clicking on it twice for each step, and the put back to zero to do it again. I still can't explain it or prove it. http://poncelet.math.nthu.edu.tw/disk3/cabrijava/c-pentagon.html
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Joined: Dec 2002
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member
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member
Joined: Dec 2002
Posts: 122 |
>Shouldn't that be "jahr"? as far as i know - yes, it should. but who knows that eccentric Durer? suppose nobody, cause he's dead :P
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Joined: Dec 2002
Posts: 122
member
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>I still can't explain it or prove it.
it would be much easier to understand and prove if there weren't so many circles :P
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Joined: Aug 2001
Posts: 10,549 Likes: 1
Carpal Tunnel
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Carpal Tunnel
Joined: Aug 2001
Posts: 10,549 Likes: 1 |
Calling all pragmatists: how to construct a regular pentagon without even a compass?
Start with a ribbon of paper. (How you construct that is a separate problem.)
Fold it into a simple overhand knot. Gently pull tight and flatten. The knot is a regular pentagon. !
(Q: What does "pragmatist" mean?
A: I don't know, but it doesn't really matter as long as I can use it properly.)
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