Re: Further expanding d[xy]/dx in the output of a Dt calculation

*To*: mathgroup at smc.vnet.net*Subject*: [mg113000] Re: Further expanding d[xy]/dx in the output of a Dt calculation*From*: Peter Breitfeld <phbrf at t-online.de>*Date*: Sun, 10 Oct 2010 06:42:39 -0400 (EDT)*References*: <i8pghf$fit$1@smc.vnet.net>

John Accardi wrote: > Hello ... any help appreciated .... > > Ref: > > http://www.accardi.com/ImplicitDifferentiationForumQuery.nb > > As you see in the *.nb cited above, during the implicit differentiation > calculation, Mathematica includes d[xy]/dx in the solution. I would > like the product differentiation rule invoked for a complete > differentiation during the Dt calculation. Then, I would hope to see > d[xy]/dx not show in the value of dy/dx in the Solve output. > > Here it is in ASCII, but it might be easier to see if you run the > notebook .... > > eq5 = x^3-x^2y+2xy^2 == 12 > Dt[eq5,x] > -3x^2 dy/dx +3x^2 + 4xy dxy/dx -6xy = 0 > Solve[%%,dy/dx] > {{dy/dx -> (3x^2 + 4xy dxy/dx -6xy)/3x^2}} > > > How can I get Mathematica to show a more complete differentiation by > expanding dxy/dx? > > > Thank you > Gianni > It seems to me, that you missed a space between x and y. xy is not x*y but a new variable //Peter -- _________________________________________________________________ Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de