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*From*: brian whatcott <betwys1@sbcglobal.net>*Date*: Mon, 23 Jun 2014 14:13:52 -0500

How about using the same notation that a math package does for this purely mechanical operation??

http://reference.wolfram.com/mathematica/ref/D.html

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[Phys-L] notation for partial derivatives

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* /From/: Carl Mungan <mungan@usna.edu <mailto:mungan%40usna.edu>>

* /Date/: Fri, 20 Jun 2014 16:05:08 -0400

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I agree with the idea that one ought to specify what variable is being held in a partial derivative if there is any possibility of confusion. eg. for f(x,y) we might want the partial of f with respect to x while y is held fixed which we would write as (curly-d f / curly-d x) subscript{y} Fine. Or maybe you prefer no parentheses, but instead a vertical bar separating the derivative and the subscript. But how would you write some harder cases? Here are two for example: 1. partial of (f/y) with respect to y while x is held fixed - specifically, where would you put the parentheses? I've seen people put the curly-d/curly-d x outside the parentheses in this case. I suppose one could put brackets and parentheses, but that starts to get ugly. 2. a second partial: say you first differentiate f with respect to x while y is held fixed, then differentiate with respect to y while x is held fixed - where now will you put parentheses and subscripts? These are just warmup examples. You can probably come up with much more gnarly examples. For example, maybe I want to specify that one is to substitute in some value such as x0 for x at some point along the way (say I have 3 variables x,y,x).

--

Carl E Mungan, Assoc Prof of Physics 410-293-6680 (O) -3729 (F)

Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363

mailto:mungan@usna.edu http://usna.edu/Users/physics/mungan/

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