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

int main()
{

  double a,b,c,d,e,f,g,h;

  a = asin(0.5);
  b = acos(0.5);
  c = atan(0.5);
  d = atan(-0.5);
  e = atan2(0.5,1.0);
  f = atan2(-0.5,1.0);
  g = atan2(0.5,-1.0);
  h = atan2(-0.5,-1.0);

  printf("a = %12.8f\n",a);
  printf("b = %12.8f\n",b);
  printf("c = %12.8f\n",c);
  printf("d = %12.8f\n",d);
  printf("e = %12.8f\n",e);
  printf("f = %12.8f\n",f);
  printf("g = %12.8f\n",g);
  printf("h = %12.8f\n",h);
}