@Kamel Boughrara 

Thank you for answering my question again.The boundary conditions in this problem that I metioned in "pdsolve_boundary_con.mw" is from a mathematic textbook and its answer is u(x,t)={exp[(-2*Pi*a/l)^2*t]}*cos(2*Pi*x/l).The codes in Maple V15's Help which solved the problem of temperature in a pole can also be find in my textbook.But I am confused about why Maple can solve the first problem(example in Help) but failing to solve the second problem(only revised the boundary conditions).Can you give me some suggestion for understanding the problem?

@Kamel Boughrara 

Thank you for answering my question again.The boundary conditions in this problem that I metioned in "pdsolve_boundary_con.mw" is from a mathematic textbook and its answer is u(x,t)={exp[(-2*Pi*a/l)^2*t]}*cos(2*Pi*x/l).The codes in Maple V15's Help which solved the problem of temperature in a pole can also be find in my textbook.But I am confused about why Maple can solve the first problem(example in Help) but failing to solve the second problem(only revised the boundary conditions).Can you give me some suggestion for understanding the problem?

@Kamel Boughrara 

pdsolve_boundary_con.mw

Here is my worksheet,in the first two lines are from Maple V15's Help"pdsolve". From line 3 is my codes,but I encountered error.

@Kamel Boughrara 

pdsolve_boundary_con.mw

Here is my worksheet,in the first two lines are from Maple V15's Help"pdsolve". From line 3 is my codes,but I encountered error.

Thank you for taking time off from work and answering my question. I refered to the example of "Partial Differential Equations: Exact Solutions Subject to Boundary Conditions" in Maple V15's help. Code in example is:

sys[4] := [diff(u(x, t), t) = k*diff(u(x, t), x, x), u(0, t) = 0, u(lambda, t) = 0, u(x,0) = f(x)];

pdsolve(sys[4]);

After running these codes,the solution is computed by constructing an infinite series and then reversed using the boundary conditions to compute a closed formula for the coefficients of the series. But when I tried replace code in the example with other boundary conditions or governing equation, Maple pointed out various Errors. I fell into confusion. Can you help me out? Thank you all the same.

Thank you for taking time off from work and answering my question. I refered to the example of "Partial Differential Equations: Exact Solutions Subject to Boundary Conditions" in Maple V15's help. Code in example is:

sys[4] := [diff(u(x, t), t) = k*diff(u(x, t), x, x), u(0, t) = 0, u(lambda, t) = 0, u(x,0) = f(x)];

pdsolve(sys[4]);

After running these codes,the solution is computed by constructing an infinite series and then reversed using the boundary conditions to compute a closed formula for the coefficients of the series. But when I tried replace code in the example with other boundary conditions or governing equation, Maple pointed out various Errors. I fell into confusion. Can you help me out? Thank you all the same.