Pity, it is a very important PDE, it is the one-dimensional wave equation. 
Nevertheless 
many thanks.

Am Donnerstag, 4. Mai 2017 00:58:05 UTC+2 schrieb Aaron Meurer:
>
> You need to use u(x, t) everywhere. SymPy considers u(x) and u(x, t) to be 
> completely different functions. 
>
> Unfortunately, pdsolve is currently not very powerful, and it is unable to 
> solve your PDE.
>
> Aaron Meurer
>
> On Wed, May 3, 2017 at 11:27 AM, <[email protected] <javascript:>> wrote:
>
>> Hi,
>> I have just started using sympy and tried to solve a PDE like this:
>>
>>
>>
>>
>>
>> My approach in sympy was:
>>
>> from sympy.solvers.pde import pdsolve
>> from sympy import Function, diff, pprint, Eq, init_printing
>> from sympy.abc import x,t,c
>> init_printing()
>> u = Function('u')
>> w = Eq(diff(u(t),t,2) - (c**2*diff(u(x),x,2)),0)
>> pdsolve(w, u(x,t),hint="all")
>>
>> Unfortunataly I've got some error-messages which I can't handle.
>> Is there any help?
>> Thanks a lot.
>>
>>
>> The error messages were:
>>
>> ValueError                                Traceback (most recent call 
>> last)<ipython-input-12-e0eef578ab5a> in <module>()----> 1 pdsolve(w, 
>> u(x,t),hint="all")
>> C:\WinPython\WinPython-32bit-3.5.2.1\python-3.5.2\lib\site-packages\sympy\solvers\pde.py
>>  in pdsolve(eq, func, hint, dict, solvefun, **kwargs)    171     # See the 
>> docstring of _desolve for more details.    172     hints = _desolve(eq, 
>> func=func,--> 173         hint=hint, simplify=True, type='pde', **kwargs)    
>> 174     eq = hints.pop('eq', False)    175     all_ = hints.pop('all', False)
>> C:\WinPython\WinPython-32bit-3.5.2.1\python-3.5.2\lib\site-packages\sympy\solvers\deutils.py
>>  in _desolve(eq, func, hint, ics, simplify, **kwargs)    224     if 
>> hints['order'] == 0:    225         raise ValueError(--> 226             
>> str(eq) + " is not a differential equation in " + str(func))    227     228  
>>    if not hints['default']:
>> ValueError: -c**2*Derivative(u(x), x, x) + Derivative(u(t), t, t) is not a 
>> differential equation in u(x, t)
>>
>>
>>
>> −c2d2dx2u(x)+d2dt2u(t)=0
>>
>>
>>
>>
>> M
>>
>>
>>
>>
>>
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>
>

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