Hi all:
I found some strange behavior in solve that's related to function
composition. Check out this short example.
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| Sage Version 4.2, Release Date: 2009-10-24 |
| Type notebook() for the GUI, and license() for information. |
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sage: var('x,t')
(x, t)
sage: f= function('f',x)
sage: e= {x:exp(t)}
sage: ft= f.subs(e); ft
f(e^t)
sage: Ft = t^2 + ft^2; Ft
t^2 + f(e^t)^2
sage: a= diff(Ft,t); a
2*e^t*f(e^t)*D[0](f)(e^t) + 2*t
sage: solve(a==0,diff(f,x).subs(e))
[D[0](f)(t) == -t*e^(-t)/f(e^t)]
Did you spot the strangeness? Somehow diff(f,x).subs(e) became diff
(f,x).subs({x:t}) after solving. Does anybody know how to fix this?
Alex
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