mirror of
https://github.com/autc04/Retro68.git
synced 2024-11-24 07:31:32 +00:00
84 lines
1.5 KiB
C
84 lines
1.5 KiB
C
|
|
/* @(#)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 */
|