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Re: Very strange behaviour of ArcTan[]

• To: mathgroup at smc.vnet.net
• Subject: [mg102666] Re: Very strange behaviour of ArcTan[]
• From: Pillsy <pillsbury at gmail.com>
• Date: Tue, 18 Aug 2009 06:07:42 -0400 (EDT)
• References: <h6bh4m$6ov$1@smc.vnet.net>

On Aug 17, 8:06 am, Alexey <lehi... at gmail.com> wrote:

> I just have discovered some strange (buggy?) feature of ArcTan[]
> function in Mathematica 5.2. Try the following;

What you've discovered is that ArcTan has a definition for two
arguments where ArcTan[x, y] gives you ArcTan[y/x], but correctly
accounting for the signs of x and y. This is actually a pretty common
bit of functionality to have access to; in the C standard library
there's a two-argument function called atan2 that does the same thing,
for instance.

Cheers,
Pillsy