Higher order total derivatives
- To: mathgroup at smc.vnet.net
- Subject: [mg81555] Higher order total derivatives
- From: janus <januswesenberg at gmail.com>
- Date: Wed, 26 Sep 2007 21:51:48 -0400 (EDT)
I am trying to avoid explicit specifying functional dependencies on
time in a dynamical system.
Total derivatives (Dt) seems like the right thing, but I can't get
Mathematica to make the right inferences for higher order derivatives.
Consider a simple example:
Block[{a, v, x, t},
t /: Dt[v, t] = a;
t /: Dt[x, t] = v;
Dt[x, {t, 2}]
]
Output:
Dt[x, {t, 2}]
What would I have to do to make Dt[x,{t,2}] come out as "a"?
Nest[Dt[#, t] &, x, 2] gives the right answer, but I would rather not
have to go this way
/Janus