If I have a method for calculating the greatest common divisor of two integers as:

public static int GCD(int a, int b)
{
    return b == 0 ? a : GCD(b, a % b);
}

What would be the best way to attach that to the System.Math class?

Here are the three ways I have come up with:

public static int GCD(this int a, int b)
{
    return b == 0 ? a : b.GCD(a % b);
}

// Lame...

var gcd = a.GCD(b);

and:

public static class RationalMath
{
    public static int GCD(int a, int b)
    {
        return b == 0 ? a : GCD(b, a % b);
    }
}

// Lame...

var gcd = RationalMath.GCD(a, b);

and:

public static int GCD(this Type math, int a, int b)
{
    return b == 0 ? a : typeof(Math).GCD(b, a % b);
}

// Neat?

var gcd = typeof(Math).GCD(a, b);

The desired syntax is Math.GCD since that is the standard for all mathematical functions.

Any suggestions? What should I do to get the desired syntax?