Re: ODE

*To*: mathgroup at smc.vnet.net*Subject*: [mg4187] Re: [mg4091] ODE*From*: WOLKOWISKY JAY H <wolkowis at euclid.Colorado.EDU>*Date*: Tue, 11 Jun 1996 00:54:57 -0400*Sender*: owner-wri-mathgroup at wolfram.com

>From: bob at zim.uoregon.edu (Robert Zimmerman) >Subject: {mg4091] ODE >Organization: University of Oregon While lectureing with Mathematica I noticed that the following ODE does not return the correct initial conditions. Is this an error or standard procedure? eq1= { x y'[x]+(x+2) y[x]==2 Exp[-x], y[0]==y0}; sol= y[x]/.(eq1// DSolve[#,y[x] ,x]&//Flatten) sol/.x->0 (*Should equal to y0 and not 1*) Out[64]= E^(-x) Out[67]= 1 (*Should equal to y0 and not 1*) The answer to your question is that x=0 is a singular point of the ODE, and so you can not specify arbitrary initial conditions. I hope this helps. Jay H. Wolkowisky ==== [MESSAGE SEPARATOR] ====