Path: chuka.playstation.co.uk!news
From: "Martin Keates" <martin@jabadaw.fsnet.co.uk>
Newsgroups: scee.yaroze.freetalk.english
Subject: Re: Sprite direction
Date: Thu, 30 Aug 2001 21:53:25 +0100
Organization: PlayStation Net Yaroze (SCEE)
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> But tan is still a really bad function to use as you will end up with divide
> by zero errors with dx/dy, use cos / arcCos.

Or, just use atan2 which takes 2 arguments and gives
an unambigious angle.

double atan2(double x, double y);

atan2(x,y) will give you an angle in the range -pi to pi
with 0 at 12 o'clock and the angle increasing clockwise.

If you're more mathematically minded, then use
atan2(y,x) which gives 0 at 3 o'clock and the angle
increasing anticlockwise.

The only domain error with it is if x and y are both 0,
which would be madness anyway. :)

Martin.