[om] Need help to encode one math expression in OpenMath!

[Bill Naylor]

> Subject: [om] Need help to encode one math expression in OpenMath!
>
> I have difficulty in encoding the following math expression in OpenMath
> .
>                                       3
>                                      d        3
>                                    ------ (x y  z)
>                                         2
>                                    dx dy
> I could not figure out how to combine nthdiff and partialdiff together.
> Any help will be appreciated.
> Thanks.

I believe that there is a problem with encoding general partial
differentiation in OpenMath given the official set of content
dictionaries. Strictly speaking youre problem is not so
bad, as I guess you can go:

                               2
                      d       d        3
                   ------ ( -----  (x y  z))
                     dy     dx dy

however what if you intended:


                                       m+n
                                      d        3
                                    ------ (x y  z)
                                      m  n
                                    dx dy

this I don't think is possible using partialdiff, possibly you could do
something using nthdiff and apply_to_list[fns2], but that's looking a bit
convoluted. I wrote an nthpartialfiff symbol, which you can get at from
the contributed CDs page:
http://monet.nag.co.uk/cocoon/openmath/cdfiles/contrib/cd/new_calculus1.html
this takes 3 arguments:

the first is a list indexing the variables
the second is a list giving the order of differentiation
the third is the function

This would allow to represent both your problem and the one I suggest
quite easily :-)

cheers,

Bill
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