Simplification / Substitution

Wolfgang Hugemann · science forum beginner Joined: 13 Mar 2006 Posts: 2

Hi,

I am doing experiments with Maxima and I experience a problem that I
have encountered with other CAS before: How do you simplify a blown-up
expression? Lets have my actual example:

ta:(vs-va)/ap;
s:va*ta + 1/2*ap*ta^2 + vs*tr + (2*vs^2 - (vs-1/2*ts*am)^2 - vc^2) /
(2*am);
r:solve(s,vs);

Gives a perfect solution, which is rather lengthy and can definitively
be written shorter by using the term

A:ap*am/(ap+am);

But I don't know how to tell Maxima to use this term. Simple approaches
by multipliction with the reciprocal of this term and then
'fullratsimp' (or something comparable) doesn't help.

I encounter this problem almost every time I am using CAS: The
experessions grow too complicated and I cannot compact them.

Any hints on general strategies?

Richard Fateman · science forum Guru Wannabe Joined: 03 May 2005 Posts: 181

Here are some suggestions. (not all specific to Maxima though..)

1. try to simplify before you do manipulations. For example, make
rational functions into polynomials by substitution of variables.

2. pre substitute... e.g.

ratsubst(1/a, (ap+am)/ap/am, s) makes s simpler.

3. try ratsubst in other ways. try factor, radcan, ratsimp.

"Wolfgang Hugemann" <google@Hugemann.de> wrote in message
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