Velocity vector thing

// my second program in C++
#include <stdio.h>
#include <math.h>
#include <iostream>
using namespace std;

int main ()
{
    double X = 6.66;
    double Y = 5.44;
    double Z = 2.33;
    double velocity;

    velocity = sqrt(pow(Z,2)+pow(Y,2)+pow(Z,2));  // actual air speed


    cout << "X speed: " << X << endl;
    cout << "Y speed: " << Y << endl;
    cout << "Z speed: " << Z << endl;

    cout.precision(3); // for 2 decimal places.

    cout << "Velocity: " << velocity << endl;

    system ("pause");
    return 0;
}