Question: 2d wave equation problem

what am i doing wrong???

> restart;
> with(PDEtools);
> a := 3;
> U := u(r, t);
> wave := a^2*(diff(U, r$2))+(diff(U, r))/r) = diff(U,t$2));
> ics := u(1, t) = 0;
> bcs := diff(U, t) = piecewise(0<= r <b,-2, b<= r<1,0), u(r, 0) = 0;
> s := pdsolve(wave, {bcs, ics});

Error, (in pdsolve/sys) too many arguments; some or all of the following are wrong: [{u(r, t)}, {u(1, t) = 0, u(r, 0) = 0, diff(u(r, t), t) = -2}]

Please Wait...