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Re: log expression not simplified


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


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