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Re: How to NDSolve the differential equation
*To*: mathgroup at smc.vnet.net
*Subject*: [mg19638] Re: How to NDSolve the differential equation
*From*: Paul Abbott <paul at physics.uwa.edu.au>
*Date*: Tue, 7 Sep 1999 00:28:35 -0400
*Organization*: University of Western Australia
*References*: <7qulo3$2r5@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
Chee Lim Cheung wrote:
> I encountered error messages with the tag Power::infy when I tried to do
> the following:
>
> NDSolve[{x y''[x] + Sin[x] y'[x] + 2 x y[x] == 0,y[0]==0, y'[0]==1}, y,
> {x,0,2}]
>
> Can anyone help me in getting Mathematica to produce an answer? I am using
> Mathematica 4.0 & Mathematica 3.0.
The error message gives a hint as to the problem -- and the solution. If you
divide
through by x and replace Sin[x]/x with 1 if x ==0, then NDSolve works fine:
NDSolve[{2 y[x] + If[x == 0, 1, Sin[x]/x] y'[x] + y''[x] == 0,
y[0] == 0, y'[0] == 1}, y, {x, 0, 2}]
____________________________________________________________________
Paul Abbott Phone: +61-8-9380-2734
Department of Physics Fax: +61-8-9380-1014
The University of Western Australia
Nedlands WA 6907 mailto:paul at physics.uwa.edu.au
AUSTRALIA http://physics.uwa.edu.au/~paul
God IS a weakly left-handed dice player
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