       Re: DSolve bug

• To: mathgroup at smc.vnet.net
• Subject: [mg97794] Re: [mg97768] DSolve bug
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Sun, 22 Mar 2009 05:45:36 -0500 (EST)

```It is just an alternate representation

Clear[f1, f2]

f1[a_][x_] := Sin[a*x]

f2[a_, x_] := Sin[a*x]

f1[c][t] == f2[c, t]

True

{Plot3D[f1[a][x], {x, 0, 2 Pi}, {a, 1, 3}],
Plot3D[f2[a, x], {x, 0, 2 Pi}, {a, 1, 3}]}

Some people prefer the f[a][x] representation to explicitly separate out
parameter(s) from argument(s)

If you prefer

DSolve[D[F[x, y, z], x, y] == 0, F[x, y, z], {x, y, z}]

{{F(x,y,z)->Subscript[c, 1][z][x]+Subscript[c, 2][z][y]}}

% /. f_[arg1_][arg2_] :> f[arg2, arg1]

{{F(x,y,z)->Subscript[c, 1][x,z]+Subscript[c, 2][y,z]}}

Bob Hanlon

On Sat, Mar 21, 2009 at 10:25 AM , Sotirios Bonanos wrote:

> Hello,
> I have encountered the following bug in DSolve:
> DSolve[D[F[x, y, z], x, y] == 0, F[x, y, z], {x, y, z}]
> gives {{F[x, y, z] -> C[z][x] + C[z][y]}}
> instead of {{F[x, y, z] -> C[x, z] + C[y, z]}}
> I don't know if this has been fixed in Mathematica 7, but it is
> present in versions 5 and 6.
> S. Bonanos http://www.inp.demokritos.gr/~sbonano/

```

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