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Re: exact integer from Log[ ]

• To: mathgroup at smc.vnet.net
• Subject: [mg58333] Re: [mg58321] exact integer from Log[ ]
• From: "Jaccard Florian" <Florian.Jaccard at he-arc.ch>
• Date: Tue, 28 Jun 2005 21:56:34 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

FullSimplify[expr] will do it !

 
F.Jaccard

-----Message d'origine-----
De : Trevor Baca [mailto:trevorbaca at gmail.com] 
Envoyé : mardi, 28. juin 2005 11:13
À : mathgroup at smc.vnet.net
Objet : [mg58321] exact integer from Log[ ]

The question is how to get the exact integer 13 when we let

  f = 880*2^(1/12)

and let

  expr = Log[2^(1/12), f/440]

with no numerics (only exact integers) in both expressions.

It seems that expr should already equal the integer 13 exactly, yet
evaluating expr gives

  (12*Log[2*2^(1/12)])/Log[2]

or

  Log[8192]/Log[2]

with Simplify[expr], which, while clearly 13 to the eye, still isn't
exactgly 13 on the page.

So how do you get 13 back out of expr, preferably without recourse to
numerics?


Trevor.