       Re: ArcTan[x,y]

• To: mathgroup at smc.vnet.net
• Subject: [mg3375] Re: ArcTan[x,y]
• From: withoff (David Withoff)
• Date: Sat, 2 Mar 1996 04:14:41 -0500
• Organization: Wolfram Research, Inc.
• Sender: owner-wri-mathgroup at wolfram.com

```In article <4h13nr\$rr4 at dragonfly.wolfram.com> Bill Freed
<billf at math.concordia.edmonton.ab.ca> writes:
> I am writing an article for a math education journal about the
> conversion to and from polar coordinates. It would be useful to know
> how the function ArcTan[x,y] is defined in Mathematica- by a single
> formula, a Which statement or whatever? A rough description or the
> Mathematica code would do.
>
> Thanks,
> William Freed
>
> billf at math.concordia.edmonton.ab.ca
>

For non-zero machine real numbers, ArcTan[x, y] calls the
C library function atan2(y, x).  If you want to know how atan2
works you might need to find someone who knows how C library
functions are typically implemented.  Probably it's a bunch
of "if" statements that eventually call something like atan(y/x)
but I don't really know.  In Mathematica, for arguments other
than non-zero machine real numbers, it's a bunch of "if"
statements that eventually call something like ArcTan[y/x].

Dave Withoff
Research and Development
Wolfram Research

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