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

#define PI 3.14159265358979323846264338327950288419716939937510
// source: http://en.wikipedia.org/wiki/Pi#Decimal_representation

int main(void) {
  printf("sin( 1/2 pi ) = %lf\n", sin(1.0/2.0*PI)); // a real number should always written like 1.0 and 2.0
  return 0;
}