Take the problem
PDE: $\quad u_{tt} = 9 u_{xx} , \qquad 0 < x < 7 , \quad t > 0$
BC: $\quad u(0,t) = u(7,t)= 0$
IC: $\quad u(x,0) = x(7-x), \qquad u_t(x,0) = 0$

Use the D'Alembert solution (remember to make the function odd and periodic) to find
$u(1,0.01) = {}$
$u(1,100) = {}$
$u(0.5,10) = {}$
$u(3.5,10) = {}$

help (numbers)