Re: combining Log[] terms
- To: mathgroup at smc.vnet.net
- Subject: [mg30500] Re: combining Log[] terms
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Fri, 24 Aug 2001 04:05:59 -0400 (EDT)
- References: <9m281v$h28$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Nicolas
The result is not valid in general
Log[1]-Log[-1]
(-I)*Pi
Log[1/-1]
I*Pi
But it does hold when a and b are both positive, and we have:
Simplify[Log[a] - Log[b], a>0&&b>0]
Log[a/b]
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
"Nicolas Bock" <nbock at acsu.buffalo.edu> wrote in message
news:9m281v$h28$1 at smc.vnet.net...
> Is there a function that combines terms like
>
> Log[a] - Log[b]
>
> to
>
> Log[a/b]?
>
> I couldn't find anything so far in the documentation regarding the
> Log[] function, only some references to Collect[], which does
> something similar to what I want for powers of a given expression.
>
> Thanks already for you help,
>
> nick
>