Вычисление определенного интеграла методом трапеций - VB

Private Sub Command1_Click()
Dim s1 As Single, s2 As Single
s1 = 0: s2 = 0
For i = 0 To 11.99 Step 0.01
 s1 = s1 + (f(i) + f(i + 0.01)) / 2 * 0.01
 s2 = s2 + Abs((f(i) + f(i + 0.01)) / 2 * 0.01)
Next i
Print s1, "без модуля"
Print s2, "с модулем"
End Sub
Function f(ByVal x As Single) As Single
e = 2.718281
f = e * Cos(x) * Cos(2 * x)
End Function