derivative of atan(x) and similar functions

"Kasper" == Kasper Kristensen <kkr at dfu.min.dk>
    on Thu, 22 Jan 2004 15:52:32 +0100 writes:

Kasper> I have added the differentiation rules for asin,
    Kasper> acos and atan to the file deriv.c.  Please let me
    Kasper> know where to send it.

Wow, that's a quick response,
thank you very much!

(Kasper has sent the file to me in the mean time).
I'll try to merge it into R-devel (where it deriv.c has been
improved in the initialization part).

Martin