Re: exact integer from Log[ ]

*To*: mathgroup at smc.vnet.net*Subject*: [mg58350] Re: exact integer from Log[ ]*From*: Peter Pein <petsie at dordos.net>*Date*: Tue, 28 Jun 2005 21:56:47 -0400 (EDT)*References*: <d9r4o7$54g$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Trevor Baca schrieb: > 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. > PowerExpand[expr] -- Peter Pein Berlin