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Re: simple question on DSolve

• To: mathgroup at smc.vnet.net
• Subject: [mg124978] Re: simple question on DSolve
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Wed, 15 Feb 2012 04:44:12 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201202141137.GAA17715@smc.vnet.net>

eqns = {y''[x] + k*y[x] == 0,
   y'[0] == yp0, y'[1] == yp1};

sol = DSolve[eqns, y, x][[1]] // Simplify

{y -> Function[{x}, (1/Sqrt[
   k])(yp0 Cos[Sqrt[k] x] Cot[Sqrt[k]] -
     yp1 Cos[Sqrt[k] x] Csc[Sqrt[k]] + yp0 Sin[Sqrt[k] x])]}

eqns /. sol // Simplify

{True, True, True}

y[x] /. sol /. {yp0 -> 0, yp1 -> 0}

0

Appears to be forced by boundary conditions.


Bob Hanlon


On Tue, Feb 14, 2012 at 6:37 AM, Gualtiero Badin
<gualtiero.badin at gmail.com> wrote:
> Hello,
> if I try to solve the simple boundary value problem
>
> y''+ky=0
> y'(0)=0
> y'(1)=0
>
> mathematica returns me y=0, that is correct but that is not the
> complete answer... Does anyone know how to get the complete answer?
> (of course i know the complete answer, but I would like to solve some
> uglier versions of the same problem...)
> Thanks

• Follow-Ups:
  • Re: simple question on DSolve
    • From: Christoph Lhotka <christoph.lhotka@fundp.ac.be>

• References:
  • simple question on DSolve
    • From: Gualtiero Badin <gualtiero.badin@gmail.com>