Hi, this might be related to:
https://trac.sagemath.org/ticket/20752 https://trac.sagemath.org/ticket/20742 (and it is doctested). Ciao, Thierry On Sat, Sep 16, 2017 at 03:17:27PM -0400, Bruno Le Floch wrote: > Hello, > > In fact, it seems that in Sage 7.2, cos((p/q)*pi) gets reduced mod pi > instead of 2pi, at least in cases where it does not simplify to square > roots: > > sage: [cos(pi*(i+13)/13) - cos(pi*i/13) > for i in range(0,50) if i%13!=0] == [0]*46 > True > > It would be good to know what fixed that bug. It might be a Ginac bug. > Perhaps cos(14*pi/9) should be added as a test of the cos function? > > Bruno > > On 09/16/2017 07:43 AM, John Cremona wrote: > > You should upgrade to a more recent version: > > > > ┌────────────────────────────────────────────────────────────────────┐ > > │ SageMath version 8.0, Release Date: 2017-07-21 │ > > │ Type "notebook()" for the browser-based notebook interface. │ > > │ Type "help()" for help. │ > > └────────────────────────────────────────────────────────────────────┘ > > sage: float(cos(14*pi/9)) > > 0.17364817766693041 > > > > > > > > On 16 September 2017 at 12:27, Mickael Pechaud <mickaelpech...@gmail.com> > > wrote: > >> Hello, > >> > >> I'm running SageMath 7.2, on a 64bits laptop with a Ubuntu 16.04.2 LTS > >> (xenial). I got a wrong answer from cos : > >> > >> sage: float(cos(14*pi/9)) > >> -0.17364817766693041 > >> > >> It should be positive - and it's inconsistent with the following lines : > >> > >> sage: float(cos(14*pi/9-2*pi)) > >> 0.17364817766693041 > >> > >> > >> sage: float(14*pi/9) > >> 4.886921905584122 > >> > >> sage: float(cos(4.886921905584122)) > >> 0.17364817766692953 > >> > >> Am I missing something, or is there an actual problem here ? > >> > >> Thanks in advance, > >> > >> Mickaël > >> > >> -- > >> You received this message because you are subscribed to the Google Groups > >> "sage-devel" group. > >> To unsubscribe from this group and stop receiving emails from it, send an > >> email to sage-devel+unsubscr...@googlegroups.com. > >> To post to this group, send email to sage-devel@googlegroups.com. > >> Visit this group at https://groups.google.com/group/sage-devel. > >> For more options, visit https://groups.google.com/d/optout. > > > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To post to this group, send email to sage-devel@googlegroups.com. > Visit this group at https://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
