problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg100302] problem*From*: parmida shabestary <dj_poni at yahoo.com>*Date*: Sun, 31 May 2009 06:36:28 -0400 (EDT)

Hi I'm having trouble solving this set of equations: y''[x] =-y[x]*((y[x])^2 + (z[x])^2)^0.5 z''[x] =-z[x]*((y[x])^2 + (z[x])^2)^0.5 I couldn't write a DSolve order for it but here is the numerical code I wrote: NDSolve[{y''[x] == -y[x]*((y[x])^2 + (z[x])^2)^0.5, z''[x] == -z[x]*((y[x])^2 + (z[x])^2)^0.5, y'[0] == 0.5, z[0] == 1, y[0] == 1, z'[0] == 0.5}, {y, z}, {x, -100, 100}] I can plot this answer but what I really need is the parametric solution(a set of equations for z and y depending on x). Please help me find the answer. thanx parmida