The arctangent is one of the more interesting trigonometry functions – and by “interesting” I of course mean a bitch to get right. I've been meaning to write something about the various methods of calculating it for a while now and finally got round to it recently.

I, ah, uhm, may have gotten a little carried away with it though ... but that's okay,! At least now I while one to recommend.

• The document itself: Off on a tangent : a look at arctangent implementations
• Related source code: trig-src.zip. Also contains decent sin(), cos() and tan() implementations.