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/* @(#)z_atan.c 1.0 98/08/13 */
/*
FUNCTION
<<atan>>, <<atanf>>---arc tangent
INDEX
atan
INDEX
atanf
ANSI_SYNOPSIS
#include <math.h>
double atan(double <[x]>);
float atanf(float <[x]>);
TRAD_SYNOPSIS
#include <math.h>
double atan(<[x]>);
double <[x]>;
float atanf(<[x]>);
float <[x]>;
DESCRIPTION
<<atan>> computes the inverse tangent (arc tangent) of the input value.
<<atanf>> is identical to <<atan>>, save that it operates on <<floats>>.
RETURNS
@ifnottex
<<atan>> returns a value in radians, in the range of -pi/2 to pi/2.
@end ifnottex
@tex
<<atan>> returns a value in radians, in the range of $-\pi/2$ to $\pi/2$.
@end tex
PORTABILITY
<<atan>> is ANSI C. <<atanf>> is an extension.
*/
/******************************************************************
* Arctangent
*
* Input:
* x - floating point value
*
* Output:
* arctan of x
*
* Description:
* This routine returns the arctan of x.
*
*****************************************************************/
#include "fdlibm.h"
#include "zmath.h"
#ifndef _DOUBLE_IS_32BITS
double
_DEFUN (atan, (double),
double x)
{
switch (numtest (x))
{
case NAN:
errno = EDOM;
return (x);
case INF:
/* this should check to see if neg NaN or pos NaN... */
return (__PI_OVER_TWO);
case 0:
return (0.0);
default:
return (atangent (x, 0, 0, 0));
}
}
#endif /* _DOUBLE_IS_32BITS */
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