## 205 Reputation

16 years, 21 days

## thank you for your help, Preben Alsholm....

thank you for your help, Preben Alsholm.
you are right,the solution for that pde doesn't exist.

BTW, I use the method you provided to another question and meet some problem.
the code is below:
> restart;
> pde := diff(u(x, t), `\$`(t, 2)) = diff(u(x, t), `\$`(x, 2));
> ibc := {u(0, t) = 0, u(1, t) = 0, u(x, 0) = sin(Pi*x), (D[2](u))(x, 0) = 3*x+1};
> res := pdsolve(pde);
> eq1 := eval(rhs(res), t = 0) = sin(Pi*x);
> eq2 := eval(diff(rhs(res), t), t = 0) = 3*x+1;
> eq1a := convert(diff(eq1, x), D);
> solve({eq2, eq1a}, {(D(_F1))(x), (D(_F2))(-x)});
> tt := `~`[map](int, %, x);
> select(has, %, _F2);
> eval(op(%), x = -x);
> -%;
> f2 := unapply(subs(%, _F2(x)), x);
> f1 := unapply(subs(op(select(has, tt, _F1)), _F1(x)), x);
> eval(res, [_F1 = f1, _F2 = f2]);
> sol := expand(%);
> pdetest(sol, [pde, op(ibc)]);
> plot3d(rhs(sol), x = 0 .. 1, t = 0 .. 2, axes = boxed);

the final result is wrong absolutely,
would you like give me some help?

one more question, in Maple, for the pde with analytic solution, Is there a general method to solve it?

## thank you for your help, Preben Alsholm....

thank you for your help, Preben Alsholm.
you are right,the solution for that pde doesn't exist.

BTW, I use the method you provided to another question and meet some problem.
the code is below:
> restart;
> pde := diff(u(x, t), `\$`(t, 2)) = diff(u(x, t), `\$`(x, 2));
> ibc := {u(0, t) = 0, u(1, t) = 0, u(x, 0) = sin(Pi*x), (D[2](u))(x, 0) = 3*x+1};
> res := pdsolve(pde);
> eq1 := eval(rhs(res), t = 0) = sin(Pi*x);
> eq2 := eval(diff(rhs(res), t), t = 0) = 3*x+1;
> eq1a := convert(diff(eq1, x), D);
> solve({eq2, eq1a}, {(D(_F1))(x), (D(_F2))(-x)});
> tt := `~`[map](int, %, x);
> select(has, %, _F2);
> eval(op(%), x = -x);
> -%;
> f2 := unapply(subs(%, _F2(x)), x);
> f1 := unapply(subs(op(select(has, tt, _F1)), _F1(x)), x);
> eval(res, [_F1 = f1, _F2 = f2]);
> sol := expand(%);
> pdetest(sol, [pde, op(ibc)]);
> plot3d(rhs(sol), x = 0 .. 1, t = 0 .. 2, axes = boxed);

the final result is wrong absolutely,
would you like give me some help?

one more question, in Maple, for the pde with analytic solution, Is there a general method to solve it?

## rewrite...

thank you very much, Markiyan Hirnyk.

## rewrite...

thank you very much, Markiyan Hirnyk.

## difference...

@Alejandro Jakubi Then, that's the difference between Maple and Mathematica.

## I know...

Ok, so, that's a problem of software engineering planning.

## suggestions...

1. The quality of commands is more important than the number of commands. Simple and useful is better.

2. Experience is the second point. Enhance the performance of basic commands is the first thing for maple, I think.

## thank you, one more question...

thank you for your method, acer,

on my computer, maple displays "Error, (in HWcall) object too large" under the command EigenConditionNumbers, how to solve it?

one more question, how to use Student[NumericalAnalysis][SpectralRadius] command to estimate the root range?

## thank you, one more question...

thank you for your method, acer,

on my computer, maple displays "Error, (in HWcall) object too large" under the command EigenConditionNumbers, how to solve it?

one more question, how to use Student[NumericalAnalysis][SpectralRadius] command to estimate the root range?

## roots on the complex plane...

Dear Markiyan Hirnyk, all roots means that some roots are complex numbers.

thank you all the same.

## roots on the complex plane...

Dear Markiyan Hirnyk, all roots means that some roots are complex numbers.

thank you all the same.

## the more competition, the better softwar...

the more competition, the better software.