BSD 4_1c_2 release

[unix-history] / usr / src / usr.lib / libm / asin.c

/*      @(#)asin.c      4.1     12/25/82        */

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

       Arctan is called after appropriate range reduction.
*/

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

double
asin(arg) double arg; {

       double sign, temp;

       sign = 1.;
       if(arg <0){
               arg = -arg;
               sign = -1.;
       }

       if(arg > 1.){
               errno = EDOM;
               return(0.);
       }

       temp = sqrt(1. - arg*arg);
       if(arg > 0.7)
               temp = pio2 - atan(temp/arg);
       else
               temp = atan(arg/temp);

       return(sign*temp);
}

double
acos(arg) double arg; {

       if((arg > 1.) || (arg < -1.)){
               errno = EDOM;
               return(0.);
       }

       return(pio2 - asin(arg));
}