Hi Christophe, On Sun, Feb 1, 2009 at 3:08 PM, Christophe Deroulers <christophe.deroulers__ggsa...@normalesup.org> wrote: > > Hello, > > Is there a way in Sage to express the derivative at one point of a > "formal" function?
There's currently no way to do this right now. I have a bit of code I started at Sage Days 13 to allow one to do this. I'll finish it up and post it tonight. For reference, there are two tickets for it at http://trac.sagemath.org/sage_trac/ticket/3914 and http://trac.sagemath.org/sage_trac/ticket/385. > Actually, I would like to be able to show with Sage that f(x+a)+f(x- > a)-2*f(x) is f''(x) at the first nonvanishing order in a, but it is > still far away from working: Sage's "taylor" does not work with a > "formal" function, and, even though Maxima does slightly better, it's > not enough: for "taylor(f(x-a),a,0,2);", Maxima's result involves "d/ > da f(x-a) |a=0", while further simplification to -f'(x) would be > needed. You should ask on the Maxima list about getting Maxima to do such a simplification natively. --Mike --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
