# [texhax] derivatives and integrals: math operators

Phil Parker phil at math.wichita.edu
Sun Aug 9 10:33:35 CEST 2009

On 08/08/2009 at 08:33 PM, Dan Hatton <vi5u0-texhax at yahoo.co.uk> wrote: >On
Thu, 6 Aug 2009, Phil Parker wrote:

>> Since we create the stuff, we get to make the rules, conventions,
>> guidelines, etc.

>It suddenly occured to me: if we want to adopt this principle (and I'm not
>_entirely_ convinced I do ;-)), I guess we need to look into how Leibniz
>typeset the "d" of differentials.  Does anyone know?

Italic, not upright. (I also teach math history, so do some research in it.)

Also at that time it was common to switch from Greek to Latin letters to
indicate taking limits. Hence \Sigma_i f(x^*_i) \delta x_i became [integral
sign] f(x) dx where Leibniz chose for [integral sign] the common Italic u.c.
"S" of the day, which is an elongated, smoothed shape that is now used only
for the integral sign. (Together with several later variants.)

Most math history texts will show some reproductions of printed pages of the
era in which this is well seen in context.

--
Phil Parker
--------------------------------------------
URL http://www.math.wichita.edu/~pparker/
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