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## [Axiom-developer] [#179 differentiating sums with respect to a bound is

 From: Bill Page Subject: [Axiom-developer] [#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.axiom-developer.org/zope/mathaction/179DifferentiatingSumsWithRespectToABoundIsWrong/diff
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--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)
-
-
-
-    _______________________________________________________
-
-
-  <http://savannah.nongnu.org/bugs/?func=detailitem&item_id=9216>
-
-_______________________________________________
-  Message sent via/by Savannah
-  http://savannah.nongnu.org/
-
\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

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