Re: ODE in mathematica. what is wrong?

*To*: mathgroup at smc.vnet.net*Subject*: [mg91320] Re: [mg91307] ODE in mathematica. what is wrong?*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Fri, 15 Aug 2008 06:54:12 -0400 (EDT)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <200808141101.HAA00111@smc.vnet.net>*Reply-to*: murray at math.umass.edu

First, insert the missing spaces between other names and y (and avoid the Subscript expressions): NDSolve[{y'[x]==-\[Rho] y[x],y[0]==y0,I \[HBar] y'[x]==\[Epsilon] y[x],y[0]==y0,y''[x]+2 \[Rho] y'[x]+k^2==0,y'[0]==g0},y,x] Second,it doesn't make sense to ask for a NUMERICAL solution, with NDSolve, unless you specify an interval: the last argument should not be x but rather something like {x,0,2}. Third, I'm suspicious of your system of differential equations, because if I ask for an exact, symbolic expression by using DSolve instead of NDSolve... DSolve[{y'[x]==-\[Rho] y[x],y[0]==y0,I \[HBar] y'[x]==\[Epsilon] y[x],y[0]==y0,y''[x]+2 \[Rho] y'[x]+k^2==0,y'[0]==g0},y[x],x] ... then I get an error DSolve::overdet "There are fewer dependent variables than equations, so the system is overdetermined." 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??? > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**References**:**ODE in mathematica. what is wrong?***From:*hoi-su jung <junghs2000@naver.com>