Re: Real roots and other assumptions...

*To*: mathgroup at smc.vnet.net*Subject*: [mg19901] Re: Real roots and other assumptions...*From*: paulh at wolfram.com (P.J. Hinton)*Date*: Mon, 20 Sep 1999 20:42:25 -0400*Organization*: "Wolfram Research, Inc."*References*: <7s3p1u$ck5@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In article <7s3p1u$ck5 at smc.vnet.net>, Janus Wesenberg <jaw at imf.au.dk> writes: >I keep encountering problems of the following type when using mathematica: >I want to solve some equation(s) under some assumptions about the unknown(s), >e.g. find the real roots of (x-1)(x^2+1). >I've tried Solve[{Im[x]==0,(x-1)(x^2+1)==0},x]] for the above problem, but that >doesn't get me anywhere. > >Is there a general way to let Mathematica know about such additional bounds as >non-complexness etc? -- if so I would be happy to know it! As of Mathematica 4, the only functions which support the ability to specify conditions on the nature of symbols are Integrate[] and Simplify[]. There is no mechanism for placing restrictions on the roots returned by solve. You can feed the result of solve to a post-processing function which tests only for real roots, provided that the values of the replacement rules are numbers. >PS. I'm using Mathematica from a HP-UX 10 system, and the notebook interface >have grave difficulties handling large expressions (they scrambled to complete >nonsense). The local system administrator just says "Use the text access", but >does anyone know how to make the notebook interface work? What do you define as "making the interface work"? Your description of the problem is too vague for any remedies to be prescribed. If you are dealing with large calculations, it is probably better to run without the notebook interface because it allows you to run the processes in the background as batch jobs. In addition, the act of formatting large expressions into two-dimensional box forms can require large amounts of resources (time and memory). If you do feel that the notebook front end is indispensible, try setting the default output format type to OutputForm instead of StandardForm (Cell -> Default Output Format Type -> OutputForm). This keeps the kernel from trying to form box expressions for its results. -- P.J. Hinton Mathematica Programming Group paulh at wolfram.com Wolfram Research, Inc. Disclaimer: Opinions expressed herein are those of the author alone.