Re: [math-fun] quintic solver safety recall, sin 1 (almost)

25 Aug 2011


      On Thu, Aug 25, 2011 at 12:09 PM, Bill Gosper <billgosper@gmail.com> wrote:
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Bill Gosper <billgosper@gmail.com> wrote:
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Rich points out that we can write a 1/5th angle formula sin a/5 =
quinticsolution(trigs(a))
Oh, foo, it's going to come down to complex 5th roots anyway:

Out[271]=
Cos[x/5] == 1/2 ((Cos[x] - I Sin[x])^(1/5) + (Cos[x] + I Sin[x])^(1/5))

In[272]:= FullSimplify[%271, \[Pi] > x > -\[Pi]]

Out[272]= True
[...]
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--rwg