```Date: Jul 20, 2013 5:54 AM
Author: Bob Hanlon
Subject: Re: f'[0]=0.5 is True?

Try starting with a fresh kernel.Clear[f, x, sol];eqn = f''[x] + 2 f'[x] + 30 f[x] == 0;eqn1 = f[0] == 1;eqn2 = f'[0] == 0.5;sol[x_] = f[x] /. DSolve[{eqn, eqn1, eqn2}, f[x], x][[1]](1.*(1.*Cos[Sqrt[29]*x] + 0.2785430072655778*           Sin[Sqrt[29]*x]))/E^xsol[0]1.sol'[0]0.5Using exact numberseqn2 = f'[0] == 1/2;sol[x_] = f[x] /. DSolve[{eqn, eqn1, eqn2}, f[x], x][[1]]((1/58)*(58*Cos[Sqrt[29]*x] + 3*Sqrt[29]*           Sin[Sqrt[29]*x]))/E^xsol[0]1sol'[0]1/2Bob HanlonOn Thu, Jul 18, 2013 at 3:00 AM, mariusz sapinski <mariusz.sapinski@gmail.com> wrote:> 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>>
```