       One more question :)

• To: mathgroup at smc.vnet.net
• Subject: [mg18318] One more question :)
• From: demiurg at lune.math.tau.ac.il (Alexander Sirotkin)
• Date: Sat, 26 Jun 1999 19:08:00 -0400
• Organization: School of Mathematical Sciences, Tel Aviv University, Israel
• Sender: owner-wri-mathgroup at wolfram.com

```Well, I seem to be flooding this newsgroup with questions, but
I really need to submit this project in AstroPhysics next week
and I promise this will be the last one :)

With help of many people from this newsgroup (thanks to everybody)
I was finally able to solve all my previous problems and actually
reduced the problem to 4 ODE...

However, there is one annoying problem - I have 4 unknown functions
and 5 ODE, that is, one of the functions (say f[x]) has two equations -
and I have to choose the correct one according to the value of f[x] :
f1'[x] == func[g[x], h[x], ...)
f1'[x] == func[g[x], h[x], ...)

f[x] = (f1[x] > f2[x] ? f1[x] : f2[x]) // plz excuse a little piece of C
code :)

So the question is - is there an elegant way of defining such a problem
in Mathematica ? (I can always divide system of equations into two sets -
with f1[x] and f2[x], solve both systems and then try to assemble all
my functions from two pieces - one from first system and the other from
second, but this is really a lot of work)