Status: New Owner: asmeurer Labels: Type-Enhancement Priority-Medium Polynomial
New issue 1557 by asmeurer: Have RootsOf.roots() divide out exact roots from expression in formal roots. http://code.google.com/p/sympy/issues/detail?id=1557 Consider this example: In [1]: list(RootsOf(x**6 - 10*x**2 + 2*x, x).roots()) Out[2]: [0, RootOf(x**6 - 10*x**2 + 2*x, x, index=1), RootOf(x**6 - 10*x**2 + 2*x, x, index=2), RootOf(x**6 - 10*x**2 + 2*x, x, index=3), RootOf(x**6 - 10*x**2 + 2*x, x, index=4), RootOf(x**6 - 10*x**2 + 2*x, x, index=5)] The quintic x**5 - 10*x + 2 is known to be unsolvable (see http://www.mathreference.com/fld- slv,xmp.html). However, the given polynomial is that quintic times x, so we know that 0 is a root. RootsOf.roots() finds that easy enough, but I think that the formal roots should be listed as RootOf(x**5 - 10*x + 2, x, index=1-5) instead of what is given now. This is what Maple does: > solve(x**6 - 10*x**2 + 2*x, x); 0, RootOf(_Z^5-10*_Z+2, index = 1), RootOf(_Z^5-10*_Z+2, index = 2), RootOf(_Z^5-10*_Z+2, index = 3), RootOf(_Z^5-10*_Z+2, index = 4), RootOf(_Z^5-10*_Z+2, index = 5) This would have many benefits. For example, you could use the discriminant (see issue 1555) to determine if any of the formal roots are repeated. -- 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-issues@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 -~----------~----~----~----~------~----~------~--~---
