AW: "Rubbish" integration outputs

*To*: mathgroup at smc.vnet.net*Subject*: [mg45730] AW: [mg45724] "Rubbish" integration outputs*From*: Klamser at t-online.de (Peter Klamser)*Date*: Thu, 22 Jan 2004 03:37:31 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi, the arbitrary variables k$XXXX are produced, because the result of your ODE contains derivates of the e^x^2 function, Mathematica can not substitute with Erf[x] neither integrate. So you have to use a numerical solution with NDSolve. Regards Peter -----Ursprüngliche Nachricht----- Von: Iwonder [mailto:yssual at yahoo.com] Gesendet: Mittwoch, 21. Januar 2004 10:55 An: mathgroup at smc.vnet.net Betreff: [mg45724] "Rubbish" integration outputs Hi, I always find me in troubles when integrating ODE that I think Mathematica should be able to do. It's all right for the very simplest, but consider for instance the following: \!\(DSolve[\((x + 2 x\^2 + x\^3)\) \(y'\)[x] + \(x\^2\) \(y''\)[x] == A, y, x]\) 'A' a constant. Well, the problem is that I don't even the clue that Mathematica *cannot* integrate it, there is some output with gibberish, like K$14646 and the like (those are intermediary variables I guess). So what is wrong? Is Mathematica expected to return such outputs? Cheers.