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[Axiomdeveloper] [#179 differentiating sums with respect to a bound is
From: 
Bill Page 
Subject: 
[Axiomdeveloper] [#179 differentiating sums with respect to a bound is wrong] (new) differentiating sums with respect to a bound is wrong 
Date: 
Wed, 22 Jun 2005 14:09:19 0500 
Changes
http://page.axiomdeveloper.org/zope/mathaction/179DifferentiatingSumsWithRespectToABoundIsWrong/diff

removed:


removed:

??changed:
 Status: None => transferred
Example of code trigerring the bug: f:=operator 'f
Status: None => transferred
Example of code trigerring the bug:
\begin{axiom}
f:=operator 'f
??changed:
 => f:=operator 'f
D(sum(f(i),i=a..x),x)



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\end{axiom}
is nonsense. The problem is in COMBF/dvdsum:
\begin{axiom}
dvdsum(l, x) ==
x = retract(y := third l)@SE => 0
k := retract(d := second l)@K
differentiate(h := third rest rest l,x) * eval(f := first l, k, h)
 differentiate(g := third rest l, x) * eval(f, k, g)
+ opdsum [differentiate(f, x), d, y, g, h]
\end{axiom}
Although this:
$$d/dx \sum_i^x f(i) = f(x)$$
is a nice try, it is wrong. It seems that the order of magnitude is
roughly correct, but that's about it.
Unfortunately, I do not know how to return the thing unevaluated,
so I cannot fix the bug yet

forwarded from http://page.axiomdeveloper.org/zope/mathaction/address@hidden