C语言库asin()函数

#include <stdio.h>
#include <math.h>

#define PI 3.14159265

int main () {
   double x, ret, val;
   x = 0.9;
   val = 180.0 / PI;

   ret = asin(x) * val;
   printf("The arc sine of %lf is %lf degrees", x, ret);

   return(0);
}