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/* @(#)z_atan2.c 1.0 98/08/13 */

/*

FUNCTION

        <<atan2>>, <<atan2f>>---arc tangent of y/x

INDEX

   atan2

INDEX

   atan2f

ANSI_SYNOPSIS

        #include <math.h>

        double atan2(double <[y]>,double <[x]>);

        float atan2f(float <[y]>,float <[x]>);

TRAD_SYNOPSIS

        #include <math.h>

        double atan2(<[y]>,<[x]>);

        double <[y]>;

        double <[x]>;

        float atan2f(<[y]>,<[x]>);

        float <[y]>;

        float <[x]>;

DESCRIPTION

<<atan2>> computes the inverse tangent (arc tangent) of <[y]>/<[x]>.

<<atan2>> produces the correct result even for angles near

@ifinfo

pi/2 or -pi/2

@end ifinfo

@tex

$\pi/2$ or $-\pi/2$

@end tex

(that is, when <[x]> is near 0).

<<atan2f>> is identical to <<atan2>>, save that it takes and returns

<<float>>.

RETURNS

<<atan2>> and <<atan2f>> return a value in radians, in the range of

@ifinfo

-pi to pi.

@end ifinfo

@tex

$-\pi$ to $\pi$.

@end tex

If both <[x]> and <[y]> are 0.0, <<atan2>> causes a <<DOMAIN>> error.

You can modify error handling for these functions using <<matherr>>.

PORTABILITY

<<atan2>> is ANSI C.  <<atan2f>> is an extension.

*/

/******************************************************************

 * Arctangent2

 *

 * Input:

 *   v, u - floating point values

 *

 * Output:

 *   arctan2 of v / u

 *

 * Description:

 *   This routine returns the arctan2 of v / u.

 *

 *****************************************************************/

#include "fdlibm.h"

#include "zmath.h"

#ifndef _DOUBLE_IS_32BITS

double

_DEFUN (atan2, (double, double),

        double v _AND

        double u)

{

  return (atangent (0.0, v, u, 1));

}

#endif /* _DOUBLE_IS_32BITS */