trouble solving partial DE

*To*: mathgroup at smc.vnet.net*Subject*: [mg39919] trouble solving partial DE*From*: karlo jolic <kjolic at swin.edu.au>*Date*: Tue, 11 Mar 2003 02:39:02 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi everyone I keeping getting the following error: NDSolve::"deql": "The first argument must have both an equation and an \ initial condition." when i try to solve the following second order partial differential equation (wherein the function u is a function of variables x and t): NDSolve[{m*D[u[x, t], t, t] + 6*Pi*n*r*D[u[x, t], t] - 0.5*mu*i*ndash*pm*((L - u[x, t])^2/(R^2 + (L - u[x, t])^2)^1.5 - 1/(R^2 + (L - u[x, t])^2)^0.5 - (L + u[x, t])^2/(R^2 + (L + u[x, t])^2)^1.5 + 1/(R^2 + (L + u[x, t])^2)^0.5) == 0, u[L, 0] == L, D[u[L, 0], t] == 0}, u, {x, 0, L}, {t, 0, 1}] I have specified 2 initial conditions already, so i can't understand why i get the error. does anyone know whats the problem? Thanks Karlo PS I'm relatively new at mathematica.