home *** CD-ROM | disk | FTP | other *** search
- Path: sparky!uunet!dtix!darwin.sura.net!jvnc.net!yale.edu!qt.cs.utexas.edu!cs.utexas.edu!torn!pulp.cs.laurentian.ca!ramsey.cs.laurentian.ca!steve
- From: steve@ramsey.cs.laurentian.ca (Stephen R. Czapor)
- Newsgroups: sci.math.symbolic
- Subject: Re: simultaneous equations.
- Summary: Please post entire system.
- Message-ID: <1992Jul28.030147.24674@ramsey.cs.laurentian.ca>
- Date: 28 Jul 92 03:01:47 GMT
- References: <1992Jul27.200213.9446@ennews.eas.asu.edu>
- Sender: news@ramsey.cs.laurentian.ca (USENET News System)
- Organization: Dept. of Computer Science, Laurentian University, Sudbury, ON
- Lines: 48
-
- In article <1992Jul27.200213.9446@ennews.eas.asu.edu> nikhil@enuxha.eas.asu.edu (Venkatesh Nikhil) writes:
- [
- [mathgroup,
- [ I need your help on the following problem.I have 8 equations as
- [follows:
- [a=P*mcp*ac*tc*tf*tr
- [b=P*mcp*(4*ac*tc*tf+ac*tc*tr+2*af*tc*tr-ac*tf*tr+ac*l*tc*tf*tr)
- [c=P*mcp*(4*ac*tc+4*af*tc+l*4*ac*tc*tf+l*ac*tc*tr+2*l*af*tc*tr-l*ac*tf*tr)
- [d=.....
- ["
- ["
- ["
- [h=..............
- [
- [I need to solve these equations simultaneously for "ac" in terms of a,b,c,d,
- [e,f,g & h. So, here i need to eliminate the other variables like P, mcp, tc,
- [tf, tr, l, L, af, etc.
- [I am using mathematica and tried the commands eliminate (but my PC ran out
- [of memory before giving me the solution) and Solve[eq,var,elim] ( but this one
- [did not work too).
- [Have any of you encountered a similar problem? Is there a way to obtain "ac" in
- [terms of just a, b, c, d, e, f, g&h eliminating the rest. I would appreciate
- [your suggestions. Is there any other software package i could use for this
- [problem?
- [ ( REST OF ARTICLE DELETED )
-
- All of the systems Macsyma, Maple and Reduce have facilities for
- solving nonlinear algebraic systems, classical elimination (via
- resultants), and Groebner bases - and, in general, all will be
- better than Mathematica's for large problems.
-
- There are, however, two things to note about your equations. For
- one, you say you have 8 equations but mention 9 variables (including
- "ac") - so you won't be able to eliminate as far as you'd like.
- For another, you should know that with systems larger than a few
- equations/variables, the chances of success are slim - unless you
- are very lucky. Even then, you will probably need far more than a
- few megabytes on a PC (unless you are very, very lucky) irrespective
- of which software you use. The fact that your equations also
- involve the parameters "a, b, ..." further complicates things.
-
- Perhaps if you posted the complete set of equations, you would
- get a more definite answer. Also, if there is any chance of
- augmenting your system with further equations, you should include
- (some of) those.
- =========================================================
- Steve Czapor, Dept. of Math. & C.S., Laurentian Univ.
- {The opinions expressed above are mine, etc.}
-