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MathGroup Archive 2002

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Re: DSolve solution validation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg33939] Re: DSolve solution validation
  • From: Gerhard Wesp <gwesp at cosy.sbg.ac.at>
  • Date: Wed, 24 Apr 2002 01:21:45 -0400 (EDT)
  • Organization: Department of Computer Science, Salzburg University
  • References: <aa3fm7$7pl$1@smc.vnet.net>
  • Reply-to: gwesp at cosy.sbg.ac.at
  • Sender: owner-wri-mathgroup at wolfram.com

Vladimir Bondarenko <vvb at mail.strace.net> wrote:
>                              DSolve[y'[z] == Abs[y[z]], y[z], z]

this is a good example where the built-in human DSolve works better than
Mathematica's :-)

y'=abs(y) has the solution y = C e^z.  depending on the sign of C, y is
either always positive or always negative.

regards,
-gerhard


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