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

/*

FUNCTION

        <<acos>>, <<acosf>>---arc cosine

INDEX

        acos

INDEX

        acosf

ANSI_SYNOPSIS

        #include <math.h>

        double acos(double <[x]>);

        float acosf(float <[x]>);

TRAD_SYNOPSIS

        #include <math.h>

        double acos(<[x]>)

        double <[x]>;

        float acosf(<[x]>)

        float <[x]>;

DESCRIPTION

        <<acos>> computes the inverse cosine (arc cosine) of the input value.

        Arguments to <<acos>> must be in the range @minus{}1 to 1.

        <<acosf>> is identical to <<acos>>, except that it performs

        its calculations on <<floats>>.

RETURNS

        @ifnottex

        <<acos>> and <<acosf>> return values in radians, in the range of 0 to pi

.

        @end ifnottex

        @tex

        <<acos>> and <<acosf>> return values in radians, in the range of <<0>> t

o $\pi$.

        @end tex

        If <[x]> is not between @minus{}1 and 1, the returned value is NaN

        (not a number) the global variable <<errno>> is set to <<EDOM>>, and a

        <<DOMAIN error>> message is sent as standard error output.

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

QUICKREF ANSI SVID POSIX RENTRANT

 acos    y,y,y,m

 acosf   n,n,n,m

MATHREF

 acos, [-1,1], acos(arg),,,

 acos, NAN,    arg,DOMAIN,EDOM

MATHREF

 acosf, [-1,1], acosf(arg),,,

 acosf, NAN,    argf,DOMAIN,EDOM

*/

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

 * Arccosine

 *

 * Input:

 *   x - floating point value

 *

 * Output:

 *   arccosine of x

 *

 * Description:

 *   This routine returns the arccosine of x.

 *

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

#include "fdlibm.h"

#include "zmath.h"

#ifndef _DOUBLE_IS_32BITS

double

_DEFUN (acos, (double),

        double x)

{

  return (asine (x, 1));

}

#endif /* _DOUBLE_IS_32BITS */