On Thu, 28 Aug 2008 13:36:53 -0700 (PDT) kcrisman <[EMAIL PROTECTED]> wrote:
> > The reciprocal of tangent is not a constant function, but Sage says > otherwise. This is now http://trac.sagemath.org/sage_trac/ticket/3980 > . > > (Incidentally, using z(x)=tan(x) also doesn't work, as it yields a > NotImplementedError (whose message could be better) for 1/z; > presumably the bug below would occur even if it were implemented, > though.) > > - kcrisman > > sage: z=tan > sage: z > tan > sage: 1/z > 1/tan > sage: find_root(1/z,1,2) > --------------------------------------------------------------------------- > RuntimeError Traceback (most recent call > last) <snip> > RuntimeError: no zero in the interval, since constant expression is > not 0. This is actually a problem with how the symbolic functions/expressions are handled. The find_root function cannot recognize that 1/z is a function. This works: sage: z = 1/tan sage: f = lambda x: z(x) sage: find_root(f,1, 2) 1.5707963267948968 and this: sage: find_root(z(x),1, 2) 1.5707963267948968 I am working on making arithmetic with function objects more intuitive, and free of these kinds of problems as a part of the effort to use ginac as a basis for symbolics. This might result in some changes to the user interface for such things, but hopefully there will be less problems of this kind. Cheers, Burcin --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
