Directional Derivatives in Mathematica
- To: mathgroup at smc.vnet.net
- Subject: [mg5694] Directional Derivatives in Mathematica
- From: "Jose M. de Aguiar" <jmaguiar at leland.Stanford.EDU>
- Date: Sat, 11 Jan 1997 14:28:59 -0500
- Organization: Stanford University
- Sender: owner-wri-mathgroup at wolfram.com
Please,
I am trying to have make mathematica to produce derivatives in terms
of directions given by vectors taken along a curve.
Let me explain:
Say I have a function w(x,y)=(r^2)*Log[r], being r the distance
between a point P(xP,yP) and a point Q(x,y) on a curve. Say {t,n} are
vectors along the tangential and normal direction along the curve.
How can I instruct mathematica to give me derivatives of the type:
w,t=(r,t)*(Log[r]) + r*(1/r)*r,t=(r,t)*(1+Log[r])
w,tn=(r,tn)*(1+Log[r]) + (r,t)*((1/r)*r,n) ?
In other words: I don't want expressions of {r,t and r,n} to be
presented in terms of {xP,x,yP,y}. I want to keep working with
them, as shown above.
Thanks for any help or suggestion on the problem.
Jose.