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## [Octave-bug-tracker] [bug #55968] [octave forge] (symbolic) Incorrect si

 From: Mike Miller Subject: [Octave-bug-tracker] [bug #55968] [octave forge] (symbolic) Incorrect simplify to sinc function Date: Thu, 21 Mar 2019 13:17:51 -0400 (EDT) User-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.75 Safari/537.36

```Follow-up Comment #5, bug #55968 (project octave):

Ok, by way of example, in Matlab:

>> rewrite(tan(x), 'sin')
ans =
- sin(x) / (2 * sin(x/2)^2 - 1)

>> rewrite(tan(x), 'sinc')
ans =
sin(x) / cos(x)

>> rewrite(tan(x), 'sinco')
ans =
sin(x) / cos(x)

>> rewrite(tan(x), 'sincos')
ans =
sin(x) / cos(x)

>> rewrite(tan(x), 'asdfasdf')
Error using rewrite (line 164)
Expected input to match one of these values:
…

In Octave

>> rewrite(tan(x), 'sin')
ans = (sym) 2*sin(x)**2/sin(2*x)

>> rewrite(tan(x), 'sinc')
ans = (sym) tan(x)

>> rewrite(tan(x), 'sinco')
ans = (sym) tan(x)

>> rewrite(tan(x), 'sincos')
ans = (sym) sin(x)/cos(x)

>> rewrite(tan(x), 'asdfasdf')
ans = (sym) tan(x)

SymPy does support "sincos". I am suggesting that if we want to be compatible
with SMT in this case, the argument to rewrite "sinc" should be treated the
same as "sincos", and whether sinc is defined normalized or unnormalized is
moot.

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Reply to this item at:

<https://savannah.gnu.org/bugs/?55968>

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