# PDE in two dependent variables

1. Sep 13, 2008

### jdstokes

That's right, I said dependent. Does anyone have any experience dealing with such beasts. I haven't been able to find a single mention of them in any textbook on PDEs.

The thing I'm really curious to know is whether the method of separation of variables works as usual, e.g. if the dep vars are f and g, can I legitamately write

$f = h(x)\varphi(y)$
$g = f(x)\psi(y)$

you may assume of course that the PDE has been linearized.

2. Sep 13, 2008

### smallphi

Those beasts are quite hard, unless you get lucky, because each beast can be viewed as PDE for one of the functions say f, with unspecified coefficients given by the other function g. This is not a single PDE but a whole family, each member given by different allowed choices of g. Since different choices of g can alter the behavior of the equation drastically, in the general case one can't expect to find the general solution: f in terms of g. You can always try separation of variables in any problem but there is no guarantee it will work. Better try the Maple PDE solver, pdsolve( ).

3. Dec 8, 2009

### spisipa1

Hey!!
I have the same kind of problem...I have a PDE in two dependent and two independent variables. Were you able to solve your problem???If so, can you please help me how to solve.
Thanks.