## maxima-bugs

 [Maxima-bugs] [ maxima-Bugs-2014392 ] solve z = x*tanh(y) + y*tanh(x) From: SourceForge.net - 2008-07-09 18:25:52 ```Bugs item #2014392, was opened at 2008-07-09 18:25 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=2014392&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 - Solving equations Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: solve z = x*tanh(y) + y*tanh(x) Initial Comment: solve([z=x*tanh(y)+tanh(x)*y], [y]); returns [y=-(x*tanh(y)-z)/tanh(x)] Which has y on both sides of the equation Why can Maxima not solve this equation ? (or if there is no solution is return an error) I believe that if z and x have fixed values, then y can be determined. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-2014392 ] solve z = x*tanh(y) + y*tanh(x) From: SourceForge.net - 2008-07-09 18:34:16 ```Bugs item #2014392, was opened at 2008-07-09 18:25 Message generated for change (Comment added) made by nobody You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&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 - Solving equations Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: solve z = x*tanh(y) + y*tanh(x) Initial Comment: solve([z=x*tanh(y)+tanh(x)*y], [y]); returns [y=-(x*tanh(y)-z)/tanh(x)] Which has y on both sides of the equation Why can Maxima not solve this equation ? (or if there is no solution is return an error) I believe that if z and x have fixed values, then y can be determined. ---------------------------------------------------------------------- Comment By: Nobody/Anonymous (nobody) Date: 2008-07-09 18:34 Message: Logged In: NO plot3d(x*tanh(y)+tanh(x)*y, [x,-5,5], [y,-5,5], [plot_format,openmath])\$ ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-2014392 ] solve z = x*tanh(y) + y*tanh(x) From: SourceForge.net - 2008-07-17 14:03:44 ```Bugs item #2014392, was opened at 2008-07-09 14:25 Message generated for change (Comment added) made by macrakis You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&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 - Solving equations Group: None Status: Open >Resolution: Rejected Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: solve z = x*tanh(y) + y*tanh(x) Initial Comment: solve([z=x*tanh(y)+tanh(x)*y], [y]); returns [y=-(x*tanh(y)-z)/tanh(x)] Which has y on both sides of the equation Why can Maxima not solve this equation ? (or if there is no solution is return an error) I believe that if z and x have fixed values, then y can be determined. ---------------------------------------------------------------------- >Comment By: Stavros Macrakis (macrakis) Date: 2008-07-17 10:03 Message: Logged In: YES user_id=588346 Originator: NO This is a transcendental equation which does not have a solution in closed form in the usual elementary functions. That is true of the simpler equations y=tanh(y), y=exp(y), etc. Remember that Maxima's solve command finds exact solutions, not approximations. Of course, for fixed z and x, you can find a numerical approximation. Take a look at the documentation for find_root. Example: find_root(y=tanh(y)+1,y,0,10); 1.961179751371539 ---------------------------------------------------------------------- Comment By: Nobody/Anonymous (nobody) Date: 2008-07-09 14:34 Message: Logged In: NO plot3d(x*tanh(y)+tanh(x)*y, [x,-5,5], [y,-5,5], [plot_format,openmath])\$ ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-2014392 ] solve z = x*tanh(y) + y*tanh(x) From: SourceForge.net - 2008-08-17 18:56:33 ```Bugs item #2014392, was opened at 2008-07-09 18:25 Message generated for change (Comment added) made by nobody You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&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 - Solving equations Group: None Status: Open Resolution: Rejected Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: solve z = x*tanh(y) + y*tanh(x) Initial Comment: solve([z=x*tanh(y)+tanh(x)*y], [y]); returns [y=-(x*tanh(y)-z)/tanh(x)] Which has y on both sides of the equation Why can Maxima not solve this equation ? (or if there is no solution is return an error) I believe that if z and x have fixed values, then y can be determined. ---------------------------------------------------------------------- Comment By: Nobody/Anonymous (nobody) Date: 2008-08-17 18:56 Message: Logged In: NO Thank you for your feedback, it was quite helpful. ---------------------------------------------------------------------- Comment By: Stavros Macrakis (macrakis) Date: 2008-07-17 14:03 Message: Logged In: YES user_id=588346 Originator: NO This is a transcendental equation which does not have a solution in closed form in the usual elementary functions. That is true of the simpler equations y=tanh(y), y=exp(y), etc. Remember that Maxima's solve command finds exact solutions, not approximations. Of course, for fixed z and x, you can find a numerical approximation. Take a look at the documentation for find_root. Example: find_root(y=tanh(y)+1,y,0,10); 1.961179751371539 ---------------------------------------------------------------------- Comment By: Nobody/Anonymous (nobody) Date: 2008-07-09 18:34 Message: Logged In: NO plot3d(x*tanh(y)+tanh(x)*y, [x,-5,5], [y,-5,5], [plot_format,openmath])\$ ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-2014392 ] solve z = x*tanh(y) + y*tanh(x) From: SourceForge.net - 2009-03-11 10:25:53 ```Bugs item #2014392, was opened at 2008-07-09 20:25 Message generated for change (Comment added) made by crategus You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&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 - Solving equations Group: None >Status: Closed Resolution: Rejected Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: solve z = x*tanh(y) + y*tanh(x) Initial Comment: solve([z=x*tanh(y)+tanh(x)*y], [y]); returns [y=-(x*tanh(y)-z)/tanh(x)] Which has y on both sides of the equation Why can Maxima not solve this equation ? (or if there is no solution is return an error) I believe that if z and x have fixed values, then y can be determined. ---------------------------------------------------------------------- >Comment By: Dieter Kaiser (crategus) Date: 2009-03-11 11:25 Message: Closing this bug report. See comment below. Dieter Kaiser ---------------------------------------------------------------------- Comment By: Nobody/Anonymous (nobody) Date: 2008-08-17 20:56 Message: Logged In: NO Thank you for your feedback, it was quite helpful. ---------------------------------------------------------------------- Comment By: Stavros Macrakis (macrakis) Date: 2008-07-17 16:03 Message: Logged In: YES user_id=588346 Originator: NO This is a transcendental equation which does not have a solution in closed form in the usual elementary functions. That is true of the simpler equations y=tanh(y), y=exp(y), etc. Remember that Maxima's solve command finds exact solutions, not approximations. Of course, for fixed z and x, you can find a numerical approximation. Take a look at the documentation for find_root. Example: find_root(y=tanh(y)+1,y,0,10); 1.961179751371539 ---------------------------------------------------------------------- Comment By: Nobody/Anonymous (nobody) Date: 2008-07-09 20:34 Message: Logged In: NO plot3d(x*tanh(y)+tanh(x)*y, [x,-5,5], [y,-5,5], [plot_format,openmath])\$ ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2014392&group_id=4933 ```