Re: Help with Identities

*To*: mathgroup at smc.vnet.net*Subject*: [mg65591] Re: [mg65585] Help with Identities*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Mon, 10 Apr 2006 02:31:11 -0400 (EDT)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

You should use Equal (==) rather than SameQ (===) Simplify[Log[x/y]==Log[x]-Log[y],#]& /@ {{x>0, y>0}, {x>0, y<0}, {x<0, y>0}, {x<0, y<0}} {True,False,True,True} {Log[x/y], Log[x]-Log[y]} /. {x->2, y->-2} {I*Pi, (-I)*Pi} Bob Hanlon > > From: "Sven C. Koehler" <schween at snafu.de> To: mathgroup at smc.vnet.net > Subject: [mg65591] [mg65585] Help with Identities > > Hello! > > As an occasional mathematican, I sometimes forget that i.e. > > Log[x/y] is very similar to Log[x] / Log[y] > > Is there some way in Mathematica to see how an mathematical > expression could look like alternatively? (Something like the opposite > of Simplify.) > > And then I wonder why > > Log[x/y] === Log[x] - Log[y] > > is False. Can I instruct Mathematica to explain why this is False? > > Best wishes, > > Sven > >