On Mar 21, 5:01 pm, Ondrej Certik <ond...@certik.cz> wrote:
> On Sat, Mar 21, 2009 at 5:58 AM, Vinzent Steinberg
>
> <vinzent.steinb...@googlemail.com> wrote:
>
> > What is the best way to replace tan(x) with sin(x)/cos(x)?
>
> > *.match() does not seem to be suited, because I don't care where tan
> > (x) occurs, I just want to replace it.
> > WildFunction() seems to be broken.
>
> That's a good question. You need to know the argument of tan(x). If
> it's just x, then:
> I would use:
>
> e.subs(tan(x), sin(x)/cos(x))
This is not general enough. Please note that you already can do
e.subs(tan, sin)
It would be great to improve this to use
a = Wild('a')
e.subs(tan(a), sin(a)/cos(a))
for replacing.
>
> I think we should maybe enhance our .match() or introduce .find() so
> that one can do e.find(tan(Wild("a"))) and it would return tan(x**2)
> or whatever is in the expression. Then you can use .subs() to
> substitute it.
>
> Ondrej
e.find() would be really useful, often you just want to find a term
and don't care whether it's nested in some other expressions.
It should be relatively easy to implement.
Vinzent
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