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## maxima-bugs

 [Maxima-bugs] [ maxima-Bugs-2359657 ] Wrong simplification of (-1)^(1/3) From: SourceForge.net - 2008-11-29 19:42:31 ```Bugs item #2359657, was opened at 2008-11-29 19:42 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2359657&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Lisp Core - Simplification Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: Wrong simplification of (-1)^(1/3) Initial Comment: The following expression is wrongly simplified: (%i54) (-1)^(1/3); (%o54) -1 We also get the wrong result with a rectform: (%i59) rectform((-1)^(1/3)); (%o59) -1 A correct result can be expressed as: %e^(1/3*%i*%pi) The numerical result would be: 0.5 + %i * 0.86602 We can force Maxima to give a correct numerical result: (%i60) (-1)^(1/3),numer; (%o60) 1.0*(-1)^0.33333333333333 To get the numerical result we have first to do a rectform: (%i61) rectform(%); (%o61) 1.0*%i*sin(0.33333333333333*%pi)+1.0*cos(0.33333333333333*%pi) (%i62) %,numer; (%o62) 0.5-0.86602540378444*%i We get a correct numerical result for a bigfloat number too, e.g. (-1.0b0)^(1/3) but not for a double float. This is reported in the bug report SF[619927]. Maxima does the wrong simplification for all rational exponents which have an odd integer in the denominator e.g 1/5, 2/5, 3/5, ... 1/7, 2/7, 3/7, ... For an even integer in the denominator an unsimplified result is returned. I think this is a serious error and I am wondering if we have further bugs related to this wrong simplification. Dieter Kaiser ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2359657&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-2359657 ] Wrong simplification of (-1)^(1/3) From: SourceForge.net - 2008-11-29 20:40:06 ```Bugs item #2359657, was opened at 2008-11-29 20:42 Message generated for change (Comment added) made by crategus You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2359657&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Lisp Core - Simplification Group: None >Status: Deleted Resolution: None Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: Wrong simplification of (-1)^(1/3) Initial Comment: The following expression is wrongly simplified: (%i54) (-1)^(1/3); (%o54) -1 We also get the wrong result with a rectform: (%i59) rectform((-1)^(1/3)); (%o59) -1 A correct result can be expressed as: %e^(1/3*%i*%pi) The numerical result would be: 0.5 + %i * 0.86602 We can force Maxima to give a correct numerical result: (%i60) (-1)^(1/3),numer; (%o60) 1.0*(-1)^0.33333333333333 To get the numerical result we have first to do a rectform: (%i61) rectform(%); (%o61) 1.0*%i*sin(0.33333333333333*%pi)+1.0*cos(0.33333333333333*%pi) (%i62) %,numer; (%o62) 0.5-0.86602540378444*%i We get a correct numerical result for a bigfloat number too, e.g. (-1.0b0)^(1/3) but not for a double float. This is reported in the bug report SF[619927]. Maxima does the wrong simplification for all rational exponents which have an odd integer in the denominator e.g 1/5, 2/5, 3/5, ... 1/7, 2/7, 3/7, ... For an even integer in the denominator an unsimplified result is returned. I think this is a serious error and I am wondering if we have further bugs related to this wrong simplification. Dieter Kaiser ---------------------------------------------------------------------- >Comment By: Dieter Kaiser (crategus) Date: 2008-11-29 21:40 Message: Deleting the report because it is not a bug. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2359657&group_id=4933 ```