#6956: cannot differentiate cotangent
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Reporter: burcin | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-4.1.2
Component: symbolics | Keywords:
Reviewer: | Author:
Merged: |
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From sage-support:
{{{
On Fri, 18 Sep 2009 13:15:46 -0500
Jason Grout <[email protected]> wrote:
> On alpha.sagenb.org, I get the following:
>
> sage: t=var('t')
> sage: diff(cot(t),t)
> D[0](cot)(t)
> sage: diff(cos(t)/sin(t),t)
> -cos(t)^2/sin(t)^2 - 1
>
>
> Does Sage not know that cot(t) is cos(t)/sin(t)?
}}}
Unfortunately it doesn't.
GiNaC doesn't define the function `cot`. Sage defines it in the file
`sage/functions/trig.py` starting at line 184. I suppose it was written
quickly by Mike during the symbolics switch.
Defining a custom derivative function (named `_derivative_`) in that
class should fix this.
Here is the thread:
http://groups.google.com/group/sage-
support/browse_thread/thread/752de34c876720cc
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6956>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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