From: SourceForge.net <no...@so...> - 2010-06-27 10:39:11
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Bugs item #3021964, was opened at 2010-06-27 11:39 Message generated for change (Tracker Item Submitted) made by hbraviner You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3021964&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 - Taylor Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Harry Braviner (hbraviner) Assigned to: Nobody/Anonymous (nobody) Summary: taylor can return wrong answer on sqrt(abs()) Initial Comment: Suppose I wish to expand sqrt(abs(r^2-1)) for large r. In the large r limit we can take r^2 -1 to be positive and abs(r^2 - 1) evaluates to r^2 - 1. I then pull out a factor of r from the sqrt() and do a Taylor expansion in negative powers of r. The series I get should be r - (1/2)*r^(-1) - (1/8) *r^(-3) + ... To do this in maxima, I should call the function taylor(sqrt(abs(r^2-1)),[r,0,3,'asymp]). However, this returns %i*r-%i/(2*r)-%i/(8*r^3)+... I believe this is because the abs() function is evaluated at r=0 (as indeed it should be if we were taking a Taylor series in positive powers of r about 0), since expanding instead around r=2 produces the same answer regardless of whether of not abs() is present. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3021964&group_id=4933 |