http://www.bartleby.com/61/87/C0788700.html[
(Interestingly, I found a site that says that the maple programming language uses ctn and another that says it uses cot - perhaps both are correct and there's been a change. One Mathematica page explicitly says it's cot AND NOT ctn in that language.)

And people are actually using the notation, too http://web.mit.edu/wwmath/calculus/differentiation/trig.html3

http://www.mansd.org/memorial/mainsite/bb/other/nhoule/subdir/math.html

What I'm not sure of is how this varies - regional, perhaps, or maybe subject area (perhaps engineers are more likely to use ctn over cot), or perhaps even temporally (in the process of changing).

Similar notational deviance in a program language would be the use of the caret for exponentiation in some languages (fortran, pascal, vb, even quickbasic) vs double asterisk (perl, and the older versions of basic). [C, for example, doesn't even HAVE an exponentiation operator! It has the exp function, but no operator!]

Another notational oddity is that for the natural logarithm. Commonly ln or LN denoted natural log, while log denoted "log base 10" unless otherwise stated. Nowadays, I've seen class notes and handouts, etc, in which log denotes "log base e" unless otherwise stated.

On a slight, er, 'tangent,' one of the most curious terminological impasses I've encountered was the definition of a "Natural Number" which has changed over the years. When a woman first indicated in a usenet group that what she learned was that the naturals were the same as the integers I thought sure she was mistaken.

The whole thread is at http://makeashorterlink.com/?H32121033

k