math problem for experts

[deanhystad]

I would like to see the C program. Should have the exact same problem.

I ran this program on Windows

#define _USE_MATH_DEFINES

#include <iostream> 
#include <cmath>

using namespace std;

int main()
{
    cout << cos(M_PI / 2);;

    return 0;
}

And the output

Output:
6.12323e-17