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Re: Factorizing...

• To: mathgroup at smc.vnet.net
• Subject: [mg74119] Re: Factorizing...
• From: Peter Pein <petsie at dordos.net>
• Date: Mon, 12 Mar 2007 04:31:24 -0500 (EST)
• References: <esr0lj$6hp$1@smc.vnet.net> <esu5qh$riq$1@smc.vnet.net> <et0no6$mq4$1@smc.vnet.net>

Bruno Campanini schrieb:
> "Jean-Marc Gulliet" <jeanmarc.gulliet at gmail.com> wrote in message 
> news:esu5qh$riq$1 at smc.vnet.net...
> 
>> Using the correct syntax strongly helps. See " The Mathematica Book
>> Online  /  A Practical Introduction to Mathematica  /  Numerical
>> Calculations  /  1.1.3 Some Mathematical Functions" at
>> http://documents.wolfram.com/mathematica/book/section-1.1.3
>>
>> In[1]:=
>> Simplify[Factor[2 + Sqrt[5]] == ((1 + Sqrt[5])/2)^3]
>>
>> [...disregard the warning message...]
>>
>> Out[1]=
>> True
> 
> I don't want to get that.
> I would like to have:
> 
> In[1]=
> Factor[2 + Sqrt[5]]
> 
> Out[1]=
> ((1 + Sqrt[5])/2)^3
> 
> instead of
> 
> Out[1]=2 + Sqrt[5]
> 
> Bruno
> 
> 

Hi Bruno,

try RootReduce:

(2 + Sqrt[5])^(1/3) // RootReduce

--> (1/2)*(1 + Sqrt[5])

Factor can not guess, wether you want sth.^3 or for instance

Expand[Sqrt[1/2 + Sqrt[5]/2]^6]

--> 2 + Sqrt[5]


hth,
Peter