Вычислить значение функции, на основе ее разложения в степенной ряд

Sub lab_4()
Dim b, y, x, s, a, c As Single
Dim n As Integer
Function Factorial(n)
  Factorial = 1
  For i = 2 To n
    Factorial = Factorial * i
  Next i
End Function
x = Val(InputBox("Ââåäèòå ''x''"))
a = x ^ 2 / Factorial
b = a * a
s = 1
For n = 1 To 110
   s = s - a * b - (c * a)
   c = a * b
Next
MsgBox (" Ñóììà ðÿäà =  " & s)
y = Cos(x)
MsgBox (" Ôóíêöèÿ =  " & y)
End Function

Sub Cos_1()
x# = CDbl(Replace(InputBox("Введите в радианах число " & Chr(34) & "x" & Chr(34) & ", где |x|<=2*PI:"), ".", ",", , , vbTextCompare))
R# = 1
S# = 1
For i& = 2 To 2000 Step 2
    S = S * x * x / (i - i * i)
    R = R + S
Next
MsgBox R
End Sub

Sub Subcos()
'Dim pi: pi = Application.WorksheetFunction.pi
Dim x, y, f, n
y = 1: f = 1: n = 0: x = 0.5
    
While n < 6
    n = n + 1: f = f * (2 * n - 1) * (2 * n)
'    MsgBox "n = " & n & "; " & "f = " & f & " = " & "(2·" & n & ")!"
    y = y + (-1) ^ n * x ^ (2 * n) / f
Wend
    
MsgBox "Приближение от Subcos:" & vbTab & y & vbCr & vbCr & _
    "Встроенный Cos(x):" & vbTab & Cos(x) & vbCr & vbCr & _
    "Разность Cos и Subcos:" & vbTab & _
    FormatNumber(Cos(x) - y, 15) & vbCr & vbCr & _
    "Количество слагаемых:" & vbTab & n
End Sub

Function myCos(x As Double, Eps As Double, Optional s As Double = 0, _
                      Optional a As Double = 0, Optional n As Double = 0) As Double
   If Abs(n) < 1 Then
      myCos = myCos(x, Eps, 1, 1, 1)
   Else
      a = -a * x * x / ((2 * n - 1) * (2 * n))
      If Abs(a) <= Eps Then
         myCos = s
      Else
         myCos = myCos(x, Eps, s + a, a, n + 1)
      End If
   End If
End Function
 
Sub Test()
    x# = 0.3
    Debug.Print myCos(x#, 0.000000000000001)
    Debug.Print Cos(x#)
End Sub