# Question:Using pdsolve with initial conditions

## Question:Using pdsolve with initial conditions

Maple

Hello,

I am trying to solve numerically the following equation :

Eq:={diff(u(x,t),t\$2)-0.1*diff(u(x,t),x\$2)+0.00001*diff(u(x,t),x\$4)+0.1*diff(u(x,t),t\$3)=0};

Here is my code :

restart;with(plots): with(PDEtools):

Eq:={diff(u(x,t),t\$2)-0.1*diff(u(x,t),x\$2)+0.00001*diff(u(x,t),x\$4)+0.1*diff(u(x,t),t\$3)=0};

BC:={u(0,t)=0,u(1,t)=0,D[1](u)(0,t)=0,D[1](u)(1,t)=0};

IC:={u(x,0)=0,D[2](u)(x,0)=piecewise(x<=0.1,0,x<=0.2,1,0),D[2,2](u)(x,O)=0};

Opts:=spacestep=1/100, timestep=1/100;

Sol:=pdsolve(Eq, IC union BC, numeric, u(x,t), Opts);

But I get the answer : "Error, (in pdsolve/numeric/match_PDEs_BCs) cannot handle systems with multiple PDE describing the time dependence of the same dependent variable, got more than one PDE for u(x,t)"

I tried without the last initial condition (D[2,2](u)(x,0)=0), and the I get "Incorrect number of initial conditions, expected 3, got 2".
So I suppose I have the right number of initial conditions, but I don't understand why It doesn't work.
If anyone has an idea...

Thanks

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