Pythagorus

lic static double Pythagorus(double a, double b)
{
    return Math.Sqrt(a * a + b * b);
}

public static double Distance(double x1, double y1, double x2, double y2)
{
    return Math.Sqrt(Math.Pow(x2 - x1, 2) + Math.Pow(y2 - y1, 2))