- From: Joris van der Hoeven <address@hidden>
- To: <address@hidden>
- Subject: RE: Derivatives in math mode
- Date: Thu, 22 May 2003 20:24:57 +0200 (CEST)
On Thu, 22 May 2003, Forringer, Ted wrote:
>
> You may type "d space y" for "d applied to y". In fact,
>
> you rather *should* type "d tab tab space y". Indeed,
>
> the upright "d" stands for the differentiation operator.
>
>
Thanks for the response, but I am afraid I still cannot get what I need.
>
>
"d <space> y" does give something that looks OK, and it would be
>
appropriate for the top of the differential because the differential
>
operator 'd/dx' is applied to 'y'. But for the 'dx' on the bottom 'd' is
>
not being applied to 'x' but the whole thing is part of one operator
>
'd/dx' so 'd <space> x' looks wrong to me.
Semantically speaking, I do not agree with you. If you write "dy/dx",
then I read "the quotient between the differentials dy and dx",
which exists if y is a function of x (check Leibniz or Newton).
Even if you consider "d/dx" as an operator, then it really is
the operator which associates "dy/dx" to "y".
>
Also, it may be a cultural difference, but every math and physics
>
textbook I have in my office uses a italic 'd' in the differentials, not
>
an upright one, so using the 'd<tab>' is not going to help me. (On my
>
system 'd<tab><tab>' gives the partial differential which is also not
>
what I am looking for.)
People took a bad habit of using the italic d, because it is more
natural to obtain with TeX/LaTeX. Nevertheless, many editors do
prefer authors to make a distinction between the operator d and
the letter d. This is best done by using a special character
for differentiation, even though you might display it in
an italic fashion. This has also been foreseen in Unicode by the way.
>
Maybe I am wrong, that is OK with me, I am just wondering 'can it be
>
done?' Can I have two letters in a row in math mode where both letters
>
are italics and there is no extra space between them?
Yes; it suffices to insert a dummy expression like an empty group.
But I am afraid that this is not what you should do here.
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