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Question: Application of chain rule to substitute in ODEs

Question:Application of chain rule to substitute in ODEs

MrBadger 4 Maple
constants
May 11 2009
0

Suppose I have an ODE:

diff(f(x,y),x$2) + diff(f(x,y),x) + diff(f(x,y),y);

now I want to re-scale the equation so z and x are given in terms of normalised lengths (zeta,xi)

xi=x/x0;

zeta=z/z0;

where x0 and z0 are constants.  On paper this would be written as a chain rule i.e.

df/dx = df/d(xi) . d(xi)/dx

I can't figure out how to get maple to do this for me using any for me.

 

Cheers
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