How to test for NaN with generics (or why NaN.Equals(NaN) == true) ?

TestNaNGenerics.cs

namespace TestForNaNWithGenerics
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using NUnit.Framework;

    [TestFixture]
    class TestForNaN
    {
        [Test]
        public void Tests()
        {
            var values = new[] { double.NaN, 42.0, 13.0, double.NaN, 666.0, double.NaN };

            var min = genericFindMin(values);
            var max = genericFindMax(values);

            Assert.AreEqual(13.0, min);
            Assert.AreEqual(666.0, max);
        }

        private bool isNaN<T>(T value) where T : IEquatable<T>
        {
            //var d = value as double?;
            //if (d.HasValue) { return double.IsNaN(d.Value); }

            return !value.Equals(value);
        }
        private bool notNaN<T>(T value) where T : IEquatable<T>
        {
            return !isNaN(value);
        }
        private T genericFindMin<T>(IEnumerable<T> values) where T: IComparable<T>, IEquatable<T>
        {
            // Test parameters
            if ((values == null) || (!values.Any())) { throw new ArgumentException("No value provided"); }

            // Remove NaNs
            var noNaNs = values.Where(notNaN);
            if (!noNaNs.Any()) { return values.First(isNaN); }

            // Work without NaNs
            var min = noNaNs.First();
            foreach (var value in noNaNs)
            {
                if (value.CompareTo(min) < 0) { min = value; }
            }

            return min;
        }
        private T genericFindMax<T>(IEnumerable<T> values) where T : IComparable<T>, IEquatable<T>
        {
            // Test parameters
            if ((values == null) || (!values.Any())) { throw new ArgumentException("No value provided"); }

            // Remove NaNs
            var noNaNs = values.Where(notNaN);
            if (!noNaNs.Any()) { return values.First(isNaN); }

            // Work without NaNs
            var max = noNaNs.First();
            foreach (var value in noNaNs)
            {
                if (value.CompareTo(max) > 0) { max = value; }
            }

            return max;
        }        
    }
}