Question: Boundary condition - Partial differential equation

Hello everybody,

I am trying to solve a partial differential equation (wave equation) with initial conditions that contain derivative and x-varying values

My equation
Uxx – Utt = 0 (hiperbólica) where xx and tt denote second partial derivatives with respect to x and t
0 <= x <= 10; t > 0;
u(0,t) = u(10,t) = 0;
Ut(x,0) = 0;
u(x,0)=
x for 0 <= x < 5
10-x for 5 <= x <= 10

I ve defined my equation as follow
> PDE := diff(u(x,t),x,x)=diff(u(x,t),t,t);

I m first trying without the x-varying initial condition.

> IBC := {u(0,t)=0,u(10,t)=0,u(x,0)=10-x,diff(u(x,0), t) = 0};
Returns the ugly

And that gives error when trying to solve
> pds := pdsolve(PDE,IBC,numeric);
Error, (in pdsolve/numeric/process_IBCs) initial/boundary condition does not contain the dependent variables of the PDE: 0 = 0

Another try with
> IBC := {u(0,t)=0,u(10,t)=0,u(x,0)=10-x,diff(u(x,t=0), t) = 0};

Looks like more promissing but returns (in a solving attempt)
> pds := pdsolve(PDE,IBC,numeric);

Error, (in pdsolve/numeric/process_IBCs) initial/boundary conditions must depend upon exactly one of the independent variables: diff(u(x, t = 0), t) = 0

Regarding the x varying initial condition, I ve tried the `assuming` keyword in various attempts but without success.

Anybody could help on the matter?

Thanks in advance for anytip.
Have a good day
Nicolas