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Re: Simplifying and Rearranging Expressions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg96031] Re: Simplifying and Rearranging Expressions
  • From: David Bailey <dave at removedbailey.co.uk>
  • Date: Mon, 2 Feb 2009 06:20:34 -0500 (EST)
  • References: <gls1u8$hjl$1@smc.vnet.net> <gm3rah$mga$1@smc.vnet.net>

John Doty wrote:
> David Park wrote:
> 
>> Nevertheless, even simple rearrangement can be difficult. I sometimes think
>> of it as doing surgery on expressions. I believe it is generally desirable
>> to use Mathematica to rearrange an expression and not retype the expression.
>> Retyping is too error prone.
> 
> In most cases, any description of how to rearrange an expression to a 
> specific form in a CAS will be more complex than a retyped expression. I 
> believe this is a theorem.
> 
> Therefore, in most cases, the easiest way will be to retype. It's not 
> error prone if you check it, e.g.:
> 
> Simplify[ retyped == original ]
> 
Testing successive transformations in this way is useful, but not all 
transformations are exact. Particularly in physics, it is common to take 
a Taylor expansion of part of an expression, or maybe even change 
notation is some subtle way.

David Bailey
http://www.dbaileyconsultancy.co.uk


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