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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

995.0. "Inscribing a regular 15-gon" by KAOA12::BARKLEY (Steve Barkley) Sun Dec 18 1988 19:10

	Gauss proved that a regular n-gon can be inscribed in a circle with
	straight-edge and compass iff n=m(2**r) where m=p1*p2*...*pk and
	each pi is a prime number of the form pi=1+2**(2**t).

	So it should be possible to inscribe a regular 15-gon in a given
	circle since 15=(2**0)*3*5.

	Does anyone know a method of constructing a regular 15-gon in a	given
	circle?

						Thanks,
							Stephen Barkley.
T.RTitleUserPersonal
Name
DateLines
995.2HERON::BUCHANANAndrew @vbo/dtn8285805/ARES,HERONSun Dec 18 1988 19:3912
>                        -< Inscribing a regular 15-gon >-
>	iff n=m(2**r) where m=p1*p2*...*pk and
>	each pi is a prime number of the form pi=1+2**(2**t).

All the pi must be distinct, as well

>	Does anyone know a method of constructing a regular 15-gon in a	given
>	circle?

Construct 5-gon, then for each point construct 3-gon including that point.

Andrew.
995.3Great! Thanks for the quick response.KAOA12::BARKLEYSteve BarkleySun Dec 18 1988 22:021