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Re: ODE in mathematica. what is wrong?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg91317] Re: ODE in mathematica. what is wrong?
*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
*Date*: Fri, 15 Aug 2008 06:53:39 -0400 (EDT)
*References*: <g813bb$4r$1@smc.vnet.net>
Hi,
the first thing whats wrong is, that
you have 3 equations for y[x] and the solution
of
y'[x] == -\[Rho]y[x]
is different form the solution
I\[HBar] y'[x] == \[Epsilon]y[x]
and has nothing to do with the solution of
y''[x] + 2 \[Rho]y'[x] + k^2 == 0
The second thing that is wrong, is that you call
NDSolve[] instead of DSolve[] and the third thing
is that you use Subscript[y,0] as initial value,
because you have said that the symbol "y" stand
for the solution function in the
ode and it can't be the solution *and* the inital value.
But
DSolve[#, y[x], x] & /@
{{y'[x] == -\[Rho] y[x],
y[0] == Subscript[\[ScriptY],
0]}, {I \[HBar] y'[x] == \[Epsilon] y[x],
y[0] == Subscript[\[ScriptY], 0]}, {y''[x] + 2 \[Rho] y'[x] +
k^2 == 0, y'[0] == Subscript[g, 0]}}
work as it should.
Regards
Jens
hoi-su jung wrote:
> Hi,
> I am a freshman of Mathematica, I need help here...
>
> I met such problem as:
>
> NDSolve[{ y'[x] == -\[Rho]y[x], y[0] == Subscript[y, 0],
> I\[HBar] y'[x] == \[Epsilon]y[x], y[0] == Subscript[y, 0],
> y''[x] + 2 \[Rho]y'[x] + k^2 == 0, y'[0] == Subscript[g, 0]}, y, x]
> NDSolve::dvnoarg: The function y appears with no arguments.
>
> How to Handle???
>
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