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From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Arctan: to use with single or with double arguments?
Date: Fri, 24 Sep 2010 14:55:49 -0700
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Date: 2010-09-24T14:55:49-07:00
List-Id: <comp.lang.ada>

On 09/24/2010 02:32 PM, Ada novice wrote:
>
> Now I know that Arctan(Y, X)  gives the result between -pi to pi while
> Arctan(Y / X)  gives the result between -pi/2 to pi/2.

There is no one-parameter Arctan defined in 
Ada.Numerics.Generic_Elementary_Functions; the parameter X has a default of 1.0, 
so what you're really calling is

Arctan (Y / X, 1.0);

Since the X parameter is positive, it's clear the result will be in quadrant I 
or IV, or -Pi/2 to Pi/2. Giving both parameters thus seems more accurate, as it 
correctly handles cases in all 4 quadrants. In addition, it is defined for X = 
0.0 (except when Y = 0.0).

HTH.

-- 
Jeff Carter
"We use a large, vibrating egg."
Annie Hall
44