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Re: Re: Inverse of "PowerExpand"

  • To: mathgroup at
  • Subject: [mg51726] Re: [mg51703] Re: Inverse of "PowerExpand"
  • From: "David Park" <djmp at>
  • Date: Sun, 31 Oct 2004 01:15:50 -0500 (EST)
  • Sender: owner-wri-mathgroup at


This brings up an interesting point about Mathematica that I think is often
troubling to new users. That is that Mathematica does not have commands for
everything, for example there is no command for complete the square. If
Mathematica had commands for everything, since mathematics and computing
applications are so broad and varied, it would end up having millions of
commands - and then you would have trouble finding the one you need.

Mathematica is not so much a tool box for doing mathematics, but a
metatoolbox for making the tools you will need to perform calculations in
your particular application.

So it is almost always necessary to make definitions or rules and do
programming while using Mathematica. Many people find it difficult to adjust
to that point of view and may spend much effort trying to find an existing
Mathematica command to do what they want, when they could much more quickly
write the necessary tool.

Of course, sometimes you may write a tool and later find that Mathematica
has it - but that is a lesser problem.

David Park
djmp at

From: Klaus G [mailto:Karl_boehme_9 at]
To: mathgroup at

> Klaus,> One method...
> Log[a] + 2*Log[b] - Log[c];
> % //. (a_.)*Log[b_] + (c_.)*Log[d_] -> Log[b^a*d^c]
> Log[(a*b^2)/c]

OK. But you assume that you know how to add logarithms..

Klaus G.

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