As for the question "html( "In which kind of school do they teach
$\\sqrt{-2.4995} = - i 1.58$ ???" );", I think any good school that teaches
about complex numbers should teach that both - i 1.58 and i 1.58
are equally valid (approximate) square roots of -2.4995. One choice is as
good as another. Any choice one makes on the whole complex plane involves
(at least) a "branch cut", cutting up the complex plane from the origin
outwards. At the branch cut, the square root function is non-continuous, so
any floating point implementation will be erratic near the branch cut (like
Sage and C are around the negative real axis). If you want to make a choice
that is different from your computer programme (such as mapping all numbers
to numbers with non-negative imaginary part), you will have to add a few
lines to the square root code that check the imaginary part of the output
and change the sign of the number if necessary.2013/5/13 <man...@gmx.net> > Could anyone shed a bit of light on this? > > The more I try, the more SAGE's types get in my way. It turns out to be > an unpredictable element. Unless I make sure *every* involved function > really returns one specific type, calculations are becoming practically > impossible, because the results are completely random (malfunctions). > > Here is just the last and most annoying of my encounters I can't make > heads or tails of, enjoy: > > http://alpha.sagenb.org/home/pub/701/ > > -- > 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 http://groups.google.com/group/sage-devel?hl=en. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- 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 http://groups.google.com/group/sage-devel?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
