Preview points to, "Square.cs(11,24): error CS0103: The name `Math' does not exist in the current context.....

namespace Treehouse.CodeChallenges
{
    class Square : Polygon
    {    
        public double SideLength { get; private set; }

        public double Area 
        {
            get
            {
                return Math.Sqrt(SideLength);
            }
        } 

        public Square(double sideLength) : base(4)
        {
            SideLength = sideLength * sideLength ;
        }    

    }
}

namespace Treehouse.CodeChallenges
{
    public class Polygon
    {
        public int NumSides { get; private set; }

        public Polygon(int numSides)
        {
            NumSides = numSides;
        }
    }
}