usr/src/old/libm/liboldnm/acos.c

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
static char sccsid[] = "@(#)acos.c      5.1 (Berkeley) %G%";
#endif not lint

/*
acos(arg) return the arccos,
        respectively of their arguments.

        Arctan is called after appropriate range reduction.
*/

#include        <errno.h>
int errno;
double atan();
double asin();
static double pio2      = 1.570796326794896619;

double
acos(arg) double arg; {

        asm("   bispsw  $0xe0");
        if(arg > 1.|| arg < -1.){
                errno = EDOM;
                return(0.);
        }

        return(pio2 - asin(arg));
}