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
>
>