Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2011

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: log expression not simplified

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115664] Re: log expression not simplified
  • From: Peter Pein <petsie at dordos.net>
  • Date: Tue, 18 Jan 2011 05:46:51 -0500 (EST)
  • References: <ih16cv$jke$1@smc.vnet.net>

On 17.01.2011 11:41, Praeceptor wrote:
> Sorry, can anybody help me understand why
>
> Simplify[Log[a/b]/Log[b/a], Assumptions ->  {a>  0, b>  a}]
>
> doesn't reduce to -1 ??
> Thanks (it's for a simple Carnot cycle calculation...)!
>

Hi,

you can use

In[1]:= Cancel[PowerExpand[Log[a/b]/Log[b/a]]]
Out[1]= -1

but please read the documentation to mind possibly unwanted effects.

This:

In[2]:= Assuming[b > a > 0,
  FunctionExpand[Log[a/b]/Log[b/a]] // Refine // Cancel]
Out[2]= -1

is a bit more typing but should be mathematically carrect in any case.

Peter


  • Prev by Date: Re: SetOptions does not work with Grid
  • Next by Date: Re: what's wrong?!!
  • Previous by thread: Re: log expression not simplified
  • Next by thread: Re: log expression not simplified