       • To: mathgroup at smc.vnet.net
• Subject: [mg31902] Re: Simple questions about Mathematica
• From: "Allan Hayes" <hay at haystack.demon.co.uk>
• Date: Mon, 10 Dec 2001 06:14:47 -0500 (EST)
• References: <9uvhm2\$ibq\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Stephen,

rl=Sqrt[a^2+b^2]\[Rule]R;

A[Sqrt[a^2+b^2]][B[Sqrt[a^2+b^2]]]/.rl

A[R][B[R]]

%/.Reverse[rl]

A[Sqrt[a^2 + b^2]][B[Sqrt[a^2 + b^2]]]

--
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

"Stephen Gray" <stevebg at adelphia.net> wrote in message
news:9uvhm2\$ibq\$1 at smc.vnet.net...
> 1. Suppose I solve some equations and get a complicated
> expression containing multiple identical elements such as
> sqrt(a^2+b^2). To make the expression smaller, clearer, and
> easier to deal with, I want to substitute say R=sqrt(a^2+b^2)
> everywhere in the main expression and have R available as
> a symbol from then on. I see nothing in Help or anywhere
> else about how to do this. But it's such a standard thing to
> do that there must be an easy answer.
>
> 2. I'm not sure how a "batch" file is suppposed to be
> prepared and fed to Mathematica. That is, I want to
> prepare a bunch of operations and variables in advance
> and feed it in, preferably having mathematica give me
> line-by-line output as it would if I were typing each line
> in  one by one.
>
>     As a new user I really need answers to these questions.
> Thanks in advance for any information.
>

```

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