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MathGroup Archive 2007

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Re: Simple ODE with time-dep BC

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77980] Re: Simple ODE with time-dep BC
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Thu, 21 Jun 2007 05:30:28 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <f5as8d$9kj$1@smc.vnet.net>

Apostolos E. A. S. Evangelopoulos wrote:
> Hello all,
> 
> I'm having 2 problems with solving the following ordinary differential equation:
> 
> h*h'[t]==-a*h^2+c
> 
> Problem 1:
> Mathematica doesn't like the form of the above:
> DSolve[{h'[t]\[Equal]-a*h[t]+c/h, h[0]\[Equal]0}, h[t], t]
===============================>!!!
Must be written h[t] rather than just h. Mathematica is perfectly 
correct in complaining and quit clear in describing the issue. The 
correct expression is

DSolve[{h'[t] == (-a)*h[t] + c/h[t], h[0] == 0}, h[t], t]

> returns
> DSolve::dvnoarg : The function h appears with no arguments. More...
[snip]

Regards,
Jean-Marc


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