Hi,
The issue occurs because the line
H(x,y,t)=x*y
redefines (silently!) x and y to be symbolic variables (and thus
independent of t).
You can check this by asking what Sage's preparser is performing on the
command H(x,y,t)=x*y before passing it to the Python interpreter: simply
type
preparse("H(x,y,t)=x*y")
The output is
'__tmp__=var("x,y,t"); H = symbolic_expression(x*y).function(x,y,t)'
The part var("x,y,t") redefines x and y as symbolic variables.
Previously, x and y were callable symbolic expressions x(t) and y(t).
Eric.
Le lundi 24 février 2025 à 11:14:24 UTC+1, bernd.bre...@gmail.com a écrit :
> Hi!
>
> I'm a newbe to sage. So please be kind if this is a beginners failure. See
> my sreenshot with the question. [image: sage.png]
>
> Thanks for your Support, Bernd
>
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