When you enter 1/4, Python evaluates this as a float. That's why all your expressions have floating point numbers. Use Rational(1, 4), or root(-1, 4). If you do that, then expand_complex() will give you the answer you want. See also http://docs.sympy.org/latest/tutorial/gotchas.html.
Aaron Meurer On Mon, Sep 5, 2016 at 7:51 PM, Richard Fateman <[email protected]> wrote: > There are 4 values for (-1)^(1/4) and there are 2 values for sqrt(-I). > > the Maxima program has a command cabs() that returns 1/2 for this > expression. > Figure out what cabs does, and you are set. :) > > > > On Sunday, September 4, 2016 at 9:16:31 AM UTC-7, bsdz wrote: >> >> Hi >> >> Can anyone recommend a way to simplify following expression? >> >> (-1)**(1/4)*sqrt(-I)/2 >> >> I would like it to return 1/2 although various methods return different >> equivalent expressions. >> >> i.e. >> >> - sp.N(_) = 0.5 # note: I don't wish to evaluate it, here >> - sp.expand_complex(_) = 0.353553390593274*sqrt(2) >> - sp.simplify(_) = 0.353553390593274*sqrt(-I)*(1 + I) >> - sp.powsimp(_) = sqrt(-I)*(0.353553390593274 + 0.353553390593274*I) >> >> Thanks >> Blair >> > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/sympy. > To view this discussion on the web visit https://groups.google.com/d/ > msgid/sympy/6ea958be-131f-4f46-96b6-2d1c80ce5e9b%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/6ea958be-131f-4f46-96b6-2d1c80ce5e9b%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6K9KkMOS8sa137k0eZuwHWoE_-FHTgAAwgkrD5ebOmtJQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
