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Fw: Re: DifferenitalD vs CapitalDifferenitalD

• To: mathgroup at smc.vnet.net
• Subject: [mg88007] Fw: [mg87939] Re: DifferenitalD vs CapitalDifferenitalD
• From: "fizzy" <fizzycist at knology.net>
• Date: Mon, 21 Apr 2008 14:39:17 -0400 (EDT)

The way this started was an Instructor friend is teaching a course in 
Fields.   He asked me why I use Mathematica rather then another product. 
  I explained and told him I would show him some examples.    One 
example I chose was to determine the Directional Derivative.   Well, 
this involves differentials.   I merely wanted to 'highlight' the 
differential visually.   I wasnt trying to use  DifferentialD as an 
operator.   Of course, I have seen DifferentialD often enough in 
integrals.   I was 'hoping' I could also use it this other way.  for 
example,  the element of path length ,

ds = Sqrt[dx^2 + dy^2 ]

I would have preferred that I could type all the 'd's here as  
DifferentialD and, of, course solve for  DifferentialDs  if I knew the 
other differentials.   But that was exactly what I couldnt do....In 
principle there is nothing 'wrong' with simply ds, dx, etc...I just 
wanted a different 'visual' on the screen.

thanks...Jerry Blimbaum


fizzy wrote:
> After applying Jens correction, I was hoping to be able to use the
> DifferentialD  with x, etc. and then use the 'dx' , where 'd' here is
> DifferentialD (just dont know how to add it here in the email),  so it 
> would be a Symbol....but this didnt work....I realize I can use the
> straight forward   dx , etc.  symbol but I want to highlight the
> Differential....any way to 'fix' this?....when I type in  
DifferentialD
> , from the Palette, and then add x to it and perform  //Head on it , it
> just returns DifferentialD
>
> thank you....jerry blimbaum
>

\[DifferentialD]x cannot be used as a symbol because \[DifferentialD] is 
treated as an operator.  A symbol name must start with a letter.

But why do you want to use \[DifferentialD]x as a symbol anyway?  I
cannot imagine any reasonable application for this.  If you explained
your motivation for wanting to have a symbol with this name, perhaps we
could say something more useful ...