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[Maxima-bugs] [ maxima-Bugs-1452341 ] solve(x^(5/2)+1, x) produces incorrect roots
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From: SourceForge.net <no...@so...> - 2006-08-15 03:33:34
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Bugs item #1452341, was opened at 2006-03-17 06:46 Message generated for change (Settings changed) made by robert_dodier You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1452341&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 Group: None Status: Open Resolution: None Priority: 5 Submitted By: Raymond Toy (rtoy) Assigned to: Nobody/Anonymous (nobody) Summary: solve(x^(5/2)+1,x) produces incorrect roots Initial Comment: Consider: (%i16) display2d:false; (%o16) false (%i17) solve(x^(5/2)+1,x); (%o17) [x = %e^(4*%i*%pi/5),x = %e^-(2*%i*%pi/5),x = %e^(2*%i*%pi/5), x = %e^-(4*%i*%pi/5),sqrt(x) = -1] (%i18) map(lambda([u],rhs(u)^(5/2)+1),%); (%o18) [2,0,0,2,%i+1] Clearly some of the roots are wrong. ---------------------------------------------------------------------- Comment By: Raymond Toy (rtoy) Date: 2006-05-15 07:35 Message: Logged In: YES user_id=28849 This fails because solvespec and solvespec1 (src/solve.lisp) tries to solve y^5+1 = 0 and then x^(1/2) = y, and assumes all the roots are actually roots. More care is needed. This is complicated because solvespec1 calls solve to find the roots, which saves them on the global variable, so we need to examine the global vars to find our roots. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1452341&group_id=4933 |