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