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MathGroup Archive 2004

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new DSolve feature

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46974] new DSolve feature
  • From: Selwyn Hollis <sh2.7183 at misspelled.erthlink.net>
  • Date: Thu, 18 Mar 2004 01:25:00 -0500 (EST)
  • References: <c387p7$bij$1@smc.vnet.net> <200403170753.CAA16766@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

The following occurs in version 5.0.1 (Mac OS X).

This works as expected:

   DSolve[x''[t] == -k x'[t] , x[t], t]

   {{x[t] -> -(C[1]/(E^(k*t)*k)) + C[2]}}

So does this:

   DSolve[{x''[t] == -k x'[t], x[0] == x0, x'[0] == 1}, x[t], t]

   {{x[t] -> (-1 + E^(k*t) + E^(k*t)*k*x0)/(E^(k*t)*k)}}

However:

   DSolve[{x''[t] == -k x'[t], x[0] == x0, x'[0] == v0}, x[t], t]

   DSolve::bvnul: For some branches of the general solution,
       the given boundary conditions lead to an empty solution.

   {}

I wonder which "branches" of it are causing the difficulty. :^)

-----
Selwyn Hollis
http://www.math.armstrong.edu/faculty/hollis
(edit reply-to to reply)


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