Expression manipulation

*To*: mathgroup at smc.vnet.net*Subject*: [mg88722] Expression manipulation*From*: David <David.B.A.Epstein at googlemail.com>*Date*: Wed, 14 May 2008 06:04:50 -0400 (EDT)

When trying to simplify an expression by hand, one carries out various kinds of steps: 1. Replace a subexpression that occurs repeatedly by a single symbol. 2. Multiply numerator and denominator of some subexpression by the same factor. 3. Cancel particular factors in numerator and denominator of some subexpression. 4. Gather together two subexpressions that were added together, and rewrite with a common denominator. 5. Remove common factors. etc. etc. etc. Using Part, one can of course access any particular subexpression. But this is time-consuming and clumsy. I find that I need trial and error to access the correct subexpression. Once I've accessed it, I often have difficulty in persuading Mathematica to perform the desired operation. And then I have trouble putting the subexpression back into place. It's something like 20 times slower than working with pencil and paper. HOWEVER pencil and paper calculations are more prone to stupid arithmetic errors, particularly if the computation is a long one. I have been unable to find a convenient way of doing this in Mathematica. I use version 5.2, but because of my University's site license, I have access to more recent versions. Would it help to change? Can anyone point me to a tutorial where experts use Mathematica to do a typical pencil and paper computation? Thanks a lot. Please copy replies to my personal email address as I don't look at the newsgroup very often. David

**Follow-Ups**:**Re: Expression manipulation***From:*Murray Eisenberg <murray@math.umass.edu>

**Re: Expression manipulation***From:*"W_Craig Carter" <ccarter@mit.edu>