Solver ' D ' cannot be used in nonlinear diffequ.

[ptc-1360488]

Nonlinear Diffequ. are solvable with MathCad, or ?
Why Do I get the report "D" cannot be used here.
See attached worksheet.

[ptc-1360488]

Sorry for the incorrect worksheet, here the better
one

[StuartBruff]

On 1/27/2010 5:55:42 AM, enricoaut wrote:
== Nonlinear Diffequ. are solvable with MathCad, or ?
== Why Do I get the report "D" cannot be used here.

It's not a particularly helpful message. It looks like your numbers 'blow up' very quickly, suggesting there is a scaling factor or some other error in the function.

Try changing the time interval to 1 to see what I mean - there are values of the order of 10¹⁰³ and 10¹⁹¹

Stuart

[ptc-1368288]

On 1/27/2010 5:41:24 AM, enricoaut wrote:
>Nonlinear Diffequ. are
>solvable with MathCad, or ?
>Why Do I get the report "D"
>cannot be used here.
>See attached worksheet.
____________________________

GENERALLY:

1. "Odesolve", solves non-linear DE's.
2. Finites differences does solve nicely.
3. Frobenius is applicable.
4. RK, RKFhelberg are applicable

HOWEVER ! ..........

1. Check for existing solutions: EQworld, CRC ...
2. Check for Lambert (W) solutions
3. Revisit the Mathsoft "Hires" example.
4. Checking the option for Radau/radau may be dramatic !

jmG