/* 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; { if(arg > 1.|| arg < -1.){ errno = EDOM; return(0.); } return(pio2 - asin(arg)); }