# [GiNaC-list] Question regarding symbolic differentiation

Felipe Bordeu Weldt felipe.bordeu at ec-nantes.fr
Sun Jul 22 19:40:16 CEST 2012

```Hello,

To do the symbolic differentiation, I created a new class, that store
the dependencies with respect to a symbol (or many) and the degree of
differentiation.

Then I can differentiate the symbol (add 1 to the degree). and at the
end I can make the substitution and the real differentiation.

I'm not sure that is the correct approach, but it works for me.

Felipe.

Le 22 juil. 12 à 19:29, Martin Ettl a écrit :

> Hello,
>
> i have a question regarding symbolic differentiation with GiNAC.
>
> Here is what i am trying to do:
>
> I have to variables a(t) and b(t), both are dependent from time (t).
> Suppose, this two variables are multiplied liked this:
>
>              a(t) * b(t)
>
> Is it possible to derive this expression (a(t)*b(t)) according time
> with ginac.
>
> The only function i found in the manual is usefull for partial
> derivation, which does not help me here.
>
>
> Here is some example code:
>
>  symbol a("a"), b("b");  // <-- how to tell ginac that variable a
> and b is dependant from variable t
>  expression f = a*b;
>  std::cout << f.diff(t,1) << std::endl;
>
>
> Many thanks in advance and best regards
>
> Martin Ettl
>
>
>
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> GiNaC-list at ginac.de
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