Hi, On Wed, Jul 22, 2009 at 11:49 PM, Bill Page<bill.p...@newsynthesis.org> wrote:
>> --------- >> h = f(x^2).diff(x)*(x+1/x) >> >> sage: h.subs(f(x^2)==1) >> 2*(x + 1/x)*x*D[0](f)(x^2) >> >> sage: h.subs(f(x^2).diff(x)==0) >> 2*(x + 1/x)*x*D[0](f)(x^2) >> --------- > > It does not make sense to ask to "substitute" 'f(x^2)=1' into 'h' > because 'f(x^2)' is an expression - not a function. May be I didn't understand you properly. Are you saying substituting an expression (f(x^2)) within an expression (h) by a constant is invalid? If so, then isn't: "(x+x^2).subs(x==1)" invalid as well? Anyway, it does not help whether you substitute by a constant or by an expression, the problem remains. Within sage the only way I know, to do above substitution is to do ------- sage: h.subs(f(x^2).diff(x)/(2*x)==0) 0 ------- However, even using such ugly tricks, I have encountered issues in substituting expression that contains new derivative. Cheers, Golam --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
