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