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f'[0]=0.5 is True?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg131392] f'[0]=0.5 is True?
  • From: mariusz sapinski <mariusz.sapinski at gmail.com>
  • Date: Thu, 18 Jul 2013 03:00:07 -0400 (EDT)
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Dear All,

I'm trying a simple exercise:

eqn = f''[x] + 2 f'[x] + 30 f[x] == 0;
Clear[f];
Clear[x];
eqn1 = f[0] == 1;
eqn2 = f'[0] == 0.5;
DSolve[{eqn, eqn1, eqn2}, f[x], x]


and I get:
DSolve::deqn: Equation or list of equations expected instead of True in the first argument {30 f[x]+2 (f^\[Prime])[x]+(f^\[Prime]\[Prime])[x]==0,f[0]==1,True}. >>

so f'[0]=0.5 is True for Mathematica?

How can it be?

If I remove eqn2 from DSolve then I get a solution with a parameter of course.

Cheers,

   Mariusz



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