Author 
Comment/Response 
VR

04/25/13 00:31am
In Response To 'Re: some trouble with DSolve'  Dear Bill,
since you have answered PDE question, I'm sending my problem to you personally:
Wave equation without boundary and initial conditions
DSolve[D[c^2*u[x, t], {x, 2}]
 D[u[x, t], {t, 2}] == 0, u[x, t], {x, t}]
gives well known solution
C[1][t  x/Sqrt[c^2]] + C[2][t + x/Sqrt[c^2]]
However, if I add these conditions
DSolve[{D[c^2*u[x, t], {x, 2}]
 D[u[x, t], {t, 2}] == 0,
u[x, 0] == Sin[Pi*x/L],
{D[u[x, t], t] /. t > 0} == 0,
u[0, t] == 0, u[L, t] == 0}, u[x, t], {x, t}]
there is no solution, DSolve is just repeated without any error messages.
Where is mistake?
URL: , 
