4. (14%) Solve the heat equation
for 0 <x< L, t>0, in which both ends are insulated: ux(0,1)=0, ux(L.t)=0 for t>0;1C:u(x,0)=f(x)
4. (14%) Solve the heat equation
for 0 <x< L, t>0, in which both ends are insulated: ux(0,1)=0, ux(L.t)=0 for t>0;1C:u(x,0)=f(x)