Hi all,

Hi all,

> deq := diff(x(t), t) = 3*x(t)/t+(9/2)*t-13;

                             d         3 x(t)   9       
                     deq := --- x(t) = ------ + - t - 13
                             dt          t      2       
> ci := x(3) = 6;

                               ci := x(3) = 6
> p := dsolve({ci, deq}, x(t), numeric);

                        p := proc(x_rkf45)  ...  end;
> plots[odeplot](p, view = [-1 .. 4, -10 .. 10]);

> p(0);

                  [                                     -8]
                  [t = 0., x(t) = 8.65023735199754930 10  ]

but if I do:

> q := dsolve({ci, deq}, x(t), type = numeric, method = taylorseries);

                    q := proc(x_taylorseries)  ...  end;
> plots[odeplot](q, view = [-1 .. 4, -10 .. 10]);


> q(0);

                             [t = 0., x(t) = 0.]
> solex := rhs(dsolve({ci, deq}, x(t)));

                                    9  2   13      3
                         solex := - - t  + -- t + t 
                                    2      2        

But in cases where I don't know the answer, which should I trust?  here is another one

> deq := diff(x(t), t) = 1-t-x(t)/t;

                               d                 x(t)
                       deq := --- x(t) = 1 - t - ----
                               dt                 t  
> ci := x(1) = 0;

                               ci := x(1) = 0
> q := dsolve({ci, deq}, x(t), numeric);

                        q := proc(x_rkf45)  ...  end;
> q(0);

                    [t = 0., x(t) = 1.73003351210698475]
> plots[odeplot](q);


> solex := rhs(dsolve({ci, deq}, x(t)));

                                    1  2   1      1 
                         solex := - - t  + - t - ---
                                    3      2     6 t
> plot(solex, t = -1 .. 1, -100 .. 100);


and for the finish

> r := dsolve({ci, deq}, x(t), numeric, method = taylorseries);

                    r := proc(x_taylorseries)  ...  end;
> plots[odeplot](r);
%;
Warning, could not obtain numerical solution at all points, plot may be incomplete

> r(0);

Error, (in r) cannot continue integration past t=0.585794295977905e-4, step size dropped below minimum

Thanks in advance for any help

Mario

Hi all,

Hi all,

I have been asked how a calculator works to calculate say exp(5) and did Maple use the same scheme.  I am sure it's a question of series but I am sure it's not a power series.  The question seemes stupid and I am ashamed for not knowing it but that's life.

Mario

Hi all,