Comment #3 on issue 1724 by nicolas.pourcelot: conjugate doesn't work for rational powers http://code.google.com/p/sympy/issues/detail?id=1724
"(-29/54 + 93**(1/2)/18) is negative, so its cubic root is complex." I understand what you mean. That's however a bit confusing, since there's a real function called cubic root, which all values are real. So, with this point of view, (-1)^(1/3) is -1, and (-27)^(1/3) is -3. "If x and y are real, then there is a unique solution and so the cube root of a real number is sometimes defined by this equation. If this definition is used, the cube root of a negative number is a negative number." cf. http://en.wikipedia.org/wiki/Cubic_root That's Maxima point of view too. (%i8) (-1)^(1/3); (%o8) -1 However, I understand that sympy defines (-1)^(1/n) as e^{i*2*pi/n}, which is the principal cube root of -1, which is more consistent for complex numbers. This leads to a double definition of cubic root for negative real numbers which is a bit confusing. Sorry for this. :-) -- You received this message because you are listed in the owner or CC fields of this issue, or because you starred this issue. You may adjust your issue notification preferences at: http://code.google.com/hosting/settings -- You received this message because you are subscribed to the Google Groups "sympy-issues" group. To post to this group, send email to sympy-iss...@googlegroups.com. To unsubscribe from this group, send email to sympy-issues+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy-issues?hl=en.
