Re: how to test if 2 expressions are the same? Mathematica 5.0

*To*: mathgroup at smc.vnet.net*Subject*: [mg46111] Re: how to test if 2 expressions are the same? Mathematica 5.0*From*: astanoff at yahoo.fr (Valeri Astanoff)*Date*: Fri, 6 Feb 2004 04:15:39 -0500 (EST)*References*: <bvt135$oj5$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

nma124 at hotmail.com (steve_H) wrote in message news:<bvt135$oj5$1 at smc.vnet.net>... > hello; > > I am confused. > > many times, I want to find if there is a way to obtain one expression > from another by tranformation. > > for example, we know that 1-sin^2(x) = cos^2(x), and a*log(x)=log(x^a), > etc.., but sometimes this does not seem to work using SameQ: > > SameQ[a Log[x], Log[x^a] ] > False > > I tried MatchQ and that also gives False. > > what is the right way to do these things in Mathematica? I checked the on-line help, > and can't seem to see the right command for this. > > many thanks, > STeve I think you have to tell Mathematica that 'a' and 'x' are positive : In[1]:=a Log[x]- Log[x^a] // Simplify[#, x>0 && a>0]& Out[1]=0 but it doesn't seem to work with SameQ!