Решение уравнения методом простых итераций - VB

Sub отделение_корней()
Dim a As Single, b As Single, h As Single, y2 As Single, x As Single, y1 As Single
a = -2: b = 2: h = 0.5: y2 = f(a)
For x = a To b Step h
y1 = y2: y2 = f(x + h)
If y1 * y2 <= 0 Then метод_итераций x, x + h
Next x
End Sub
Function f(x As Single) As Single
  f = (1 + Cos(x)) / (3 - Sin(x)) - 0.5
End Function
Function f1(x As Single) As Single
  f1 = 1 / (2 * Sqr(x)) * 2 * x
End Function
Sub метод_итераций()
  Const e = 0.0001
  Dim x As Single, x1 As Single, q As Single, e0 As Single
  x = 0.3
Do
  x1 = x: x = f(x)
  Loop While Abs(x - x1) > e
  q = f1(x)
  If q > 0 Then e0 = e * q / (1 - q) Else e0 = e
  Debug.Print x, e0
End Sub