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Re: mixed partial derivatives

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91278] Re: mixed partial derivatives
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 13 Aug 2008 04:39:42 -0400 (EDT)
  • References: <g7rij3$i8v$1@smc.vnet.net>

Hi,

X[-3, v] == X[3, v]

will not work with mixed derivatives aspecial on the
interval u in [0,3] and not u in [-3,3]
and your equation is singular.

Regards
   Jens

Narasimham wrote:
> When mixed derivatives are not allowed, what is the fix? TIA
> 
> p=D[X[u,v],u]; q=D[X[u,v],v]; r =D[X[u,v],u,u]; s=D[X[u,v],u,v];
> t=D[X[u,v],v,v];
> GC[u_,v_] = (r t - s^2)/(1+p^2 + q^2)^2
> NDSolve[{GC[u,v]==  1, X[u, 0] == Cosh[u], Derivative[0,1][X][u, 0] ==
> 0,
>         X[-3, v] == X[3, v]},X[u,v], {u,0,3},{v,0,3}]
> 
> Narasimham
> 


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