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

double square(double x) {
    return x*x; 
}

int main() {
    int x = 4; 
    printf("hello, world, my number is %d\n", x);
    x = 5;
    printf("now my number is %d\n", x);

    double t = 3.14;
    double z = sin(t);
    printf("sin of %f is %f\n", t, z);
    
    printf("square of %f is %f\n", t, square(t));
     
    return 0;
}