RE: newbie question: generic derivatives
- To: mathgroup at smc.vnet.net
- Subject: [mg41582] RE: [mg41563] newbie question: generic derivatives
- From: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>
- Date: Tue, 27 May 2003 05:25:30 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
>-----Original Message----- >From: bardino at mail.com [mailto:bardino at mail.com] To: mathgroup at smc.vnet.net >Sent: Tuesday, May 27, 2003 7:47 AM >To: mathgroup at smc.vnet.net >Subject: [mg41582] [mg41563] newbie question: generic derivatives > > >Hello all. > >I'm new to mathematica and i'm trying to do some partial derivatives. > >I have y(x) and f(y,y') and would like to get: > >df/dx=... > >Is there a way to get a result without defining 'f' and 'y'. I mean >df/dx = pf/py y' + pf/py' y''. > >Thanks in advance, >-Eduardo > Not clear to me, what you mean "defining"? If you look at this in StandardForm (or TraditionalForm), it's there, right before your eyes In[6]:= Dt[f[y[x], y'[x]], x] // InputForm Out[6]//InputForm= Derivative[2][y][x]*Derivative[0, 1][f][y[x], Derivative[1][y][x]] + Derivative[1][y][x]* Derivative[1, 0][f][y[x], Derivative[1][y][x]] As you possibly don't have Mathematica at your hands, StandardForm looks something like this: (0, 1) (1, 0) y''[x] f [y[x], y'[x]] + y'[x] f [y[x], y'[x]] -- Hartmut