[Octave-bug-tracker] [bug #55968] [octave forge] (symbolic) Incorrect simplify to sinc function

[Mike Miller]

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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