DecimalSqrt

    Public Function DecimalSqrt(ByVal Number As Decimal, _
                                Optional ByVal guess As Nullable(Of Decimal) = Nothing) As Decimal
        Dim ourGuess As Decimal = guess.GetValueOrDefault(Number / 2D)
        Dim result As Decimal = Number / ourGuess
        Dim average As Decimal = (ourGuess + result) / 2D
        If average = ourGuess Then Return average Else Return DecimalSqrt(Number, average)
    End Function