using System.Math;

class Program
{
    delegate double MyCos(double x);
    static void Main(string[] args)
    {
        MyCos cos = new MyCos(Math.Cos);
        Console.WriteLine(cos(Math.PI));
    }
}

Imports System.Math
Module Module1
    Sub Main()
        Console.WriteLine(Cos(PI))
    End Sub
End Module