maxima-bugs

 [Maxima-bugs] [ maxima-Bugs-2843954 ] limit of trig expression From: SourceForge.net - 2009-08-25 00:42:17 ```Bugs item #2843954, was opened at 2009-08-24 19:42 Message generated for change (Tracker Item Submitted) made by willisbl You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2843954&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 - Limit Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Barton Willis (willisbl) Assigned to: Nobody/Anonymous (nobody) Summary: limit of trig expression Initial Comment: (%i55) e : (2*sin(x)*z+cos(x)*sin(2*x)-2*cos(x)^2*sin(x))/(z^2+(-sin(2*x)^2-4*sin(x)^2-cos(x)^2-1)*z+sin(2*x)^2-4*cos(x)*sin(x)*sin(2*x)+4*cos(x)^2*sin(x)^2); (%o55) (2*sin(x)*z+cos(x)*sin(2*x)-2*cos(x)^2*sin(x))/(z^2+(-sin(2*x)^2-4*sin(x)^2-cos(x)^2-1)*z+sin(2*x)^2-4*cos(x)*sin(x)*sin(2*x)+4*cos(x)^2*sin(x)^2) (%i56) limit(e,z,0); (%o56) cos(x)/(sin(2*x)-2*cos(x)*sin(x)) Bogus: (%i57) trigexpand(%); Division by 0 -- an error. To debug this try debugmode(true); OK: (%i58) limit(trigexpand(e),z,0); (%o58) -(2*sin(x))/((4*cos(x)^2+4)*sin(x)^2+cos(x)^2+1) ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2843954&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-2843954 ] limit of trig expression From: SourceForge.net - 2010-03-26 01:05:24 ```Bugs item #2843954, was opened at 2009-08-24 20:42 Message generated for change (Comment added) made by rtoy You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2843954&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 - Limit Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Barton Willis (willisbl) Assigned to: Nobody/Anonymous (nobody) Summary: limit of trig expression Initial Comment: (%i55) e : (2*sin(x)*z+cos(x)*sin(2*x)-2*cos(x)^2*sin(x))/(z^2+(-sin(2*x)^2-4*sin(x)^2-cos(x)^2-1)*z+sin(2*x)^2-4*cos(x)*sin(x)*sin(2*x)+4*cos(x)^2*sin(x)^2); (%o55) (2*sin(x)*z+cos(x)*sin(2*x)-2*cos(x)^2*sin(x))/(z^2+(-sin(2*x)^2-4*sin(x)^2-cos(x)^2-1)*z+sin(2*x)^2-4*cos(x)*sin(x)*sin(2*x)+4*cos(x)^2*sin(x)^2) (%i56) limit(e,z,0); (%o56) cos(x)/(sin(2*x)-2*cos(x)*sin(x)) Bogus: (%i57) trigexpand(%); Division by 0 -- an error. To debug this try debugmode(true); OK: (%i58) limit(trigexpand(e),z,0); (%o58) -(2*sin(x))/((4*cos(x)^2+4)*sin(x)^2+cos(x)^2+1) ---------------------------------------------------------------------- >Comment By: Raymond Toy (rtoy) Date: 2010-03-25 21:05 Message: I think limit basically evaluates the limit of the numerator and denominator. It thinks there are are no problems with either because the terms without z look fine, but, in fact, are exactly zero for all x. Not sure what can be done in this case. I do see that in limitsimp there is a hack to handle sin(x)^2+cos(x)^2. I suppose we could do trigexpand in addition to the hack, but that seems as if it could potentially complicate limit a lot. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2843954&group_id=4933 ```

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