8 Sep
2005
8 Sep
'05
3:11 p.m.
On Thursday 08 September 2005 20:56, Eugene Salamin wrote:
Let w = exp(2 pi i/5). Then the denesting identity is true for the fifth root r = 7^(1/5)w^k only if Re(sqrt(8-r)) is chosen negative when k = 2 or 3, and positive in the other three cases.
And is there some obvious (to those sufficiently initiated) reason why? I'm guessing the Right Way to describe this is in terms of the Legendre symbol (k/5), but just how that works out is not at all clear to me. -- g