Newsgroups: geometry.research
From: haoyuep@aol.com (Dan Hoey)
Date: 16 Jul 2001 13:50:54 -0400
Subject: Re: exact value of sin(pi/7)

Andrew Weimholt <and...@weimholt.com> writes:
> You probably weren't dreaming. Eric Weistein's "CRC Concise
> Encyclopedia of Mathematics" gives several exact values for
> sin(pi*a/b) including sin(pi/7). Unfortunately the text is
> no longer available online, and I don't have my copy of the
> book with me. I recall it was a fairly complicated expression
> cointaining nested roots. I believe the text also showed the
> derivation.

Well, there's ((-1)^(5/14) - (-1)^(9/14))/2, but that seems
like cheating to me.  I wonder if there's a solution in real
roots.  If you find your treasure trove, please let us know
what it said.

Dan
haoyuep@aol.com