Re: ridiculous results with DSolve
- To: mathgroup at smc.vnet.net
- Subject: [mg33371] Re: [mg33363] ridiculous results with DSolve
- From: BobHanlon at aol.com
- Date: Mon, 18 Mar 2002 00:18:48 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
In a message dated 3/17/02 7:39:09 AM, diego_catalano_ferraioli at yahoo.com
writes:
>Actually I'm interested in implementation of algoritms based on the Lie
>
>theory of differential equations.
>I was searching for a suitable language for an efficient implementation
>
>of these algoritms when I discovered that (for example):
> if you try to solve with Mathematica the trivial PDE
>
>
>D[u[x,y],x,x]==0
>
> then a Dump occurs, but if you try to solve the equivalent equation
>
>
>D[u[x,y],y,y]==0
>
> then Mathematica gives the wrong solution
>
> u[x,y]=
>C[1][x]+C[2][y] .
>
>This result is ridiculous !!!!
>How it is possible?
>
Works fine on my system
$Version
4.1 for Mac OS X (November 5, 2001)
DSolve[D[u[x,y],x,x]==0, u[x,y], {x,y}]
{{u[x, y] -> C[1][y] + x*C[2][y]}}
DSolve[D[u[x,y],{x,2}]==0, u[x,y], {x,y}]
{{u[x, y] -> C[1][y] + x*C[2][y]}}
DSolve[D[u[x,y],y,y]==0, u[x,y], {x,y}]
{{u[x, y] -> C[1][x] + y*C[2][x]}}
DSolve[D[u[x,y],{y,2}]==0, u[x,y], {x,y}]
{{u[x, y] -> C[1][x] + y*C[2][x]}}
Bob Hanlon
Chantilly, VA USA