higher derivatives of implicit equation? - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: higher derivatives of implicit equation? (/thread-9091.html) higher derivatives of implicit equation? - DrD - 09-16-2017 11:33 AM Can higher order derivatives be obtained in CAS, (without programming)? Example: z:=(3*x^2-y^2) = 16, simplify(implicit_diff(z,x,y)) leads to 3*x /y as the first derivative of z. How would one obtain the (Second derivative): d^2y/dx^2=(3*y-3*x*3*x/y)/y^2 (or simplified equivalent)? -Dale- RE: higher derivatives of implicit equation? - Tim Wessman - 09-16-2017 05:52 PM simplify(implicit_diff(z,x,y,2)) works for me on the latest version. So next update (if any) should have it being very simple at least. RE: higher derivatives of implicit equation? - DrD - 09-16-2017 07:13 PM Thank you kind sir. (I should have thought to try that!) -Dale- RE: higher derivatives of implicit equation? - melkhouly - 09-18-2017 10:00 AM I have tried that on my Prime with software 2017 07 10 (12066) and cas 1.1.2-11 and the command implicit_diff(z,x,y,2) gace Error Bad Argument Value RE: higher derivatives of implicit equation? - Helge Gabert - 09-18-2017 09:17 PM Yes, we mere mortals will have to wait for the next firmware update (if any!) . . . maybe more XCAS commands will be implemented as well, as discussed here http://www.hpmuseum.org/forum/thread-8577.html?highlight=xcas RE: higher derivatives of implicit equation? - parisse - 09-19-2017 06:04 AM In the meantime, you can enter this program: Code: ``` idiff(eq,x,y,n):=begin   local j,dn,d1;   d1:=-diff(eq,x)/diff(eq,y);   dn:=d1;   for j from 2 to n do     dn:=diff(dn,x)+diff(dn,y)*d1;   end;   return dn; end``` RE: higher derivatives of implicit equation? - Helge Gabert - 09-20-2017 02:32 PM Great! Just two minor modifications. In order to run on the Prime current firmware, 1) n=1 in the first line gives an error message "unable to eval test in loop . . . " and ought to be replaced by n 2) eq should not be entered as an equation, but as an expression, in order to avoid the =undef RE: higher derivatives of implicit equation? - parisse - 09-21-2017 12:38 PM I have edited the n=1 (default argument not available in current firmware).