Алгоритмы итеративных циклических стурктур

Option Strict On
Option Explicit On
Imports System.Math
Public Class Form1
    Function vvod(ByVal T As TextBox) As Double
        Return Val(T.Text)
    End Function
    Sub vivod(ByVal Z As Double, ByVal t As TextBox)
        t.Text = CStr(Z)
    End Sub
    Sub vivodlist(ByVal Z As Double, ByVal LB As ListBox)
        LB.Items.Add(CStr(Z))
    End Sub
    Function posledovatelnost(ByVal x As Double, ByVal eps As Double) As Double
        Dim a, s As Double
        Dim n As Integer = 0
        a = x
        s = 0
        Do Until Abs(a) < eps Or n > 100
            a = (-1) ^ n * x ^ 2 / (2 * n + 1) * (2 * n + 2)
            s = s + a
            n = n + 1
            vivodlist(n, ListBox1)
            vivodlist(a, ListBox2)
        Loop
        Return s
    End Function
    Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
        Dim eps, x As Double
        eps = vvod(TextBox1)
        x = vvod(TextBox2)
        posledovatelnost(x, eps)
        vivod(Cos(x), TextBox3)
    End Sub
    Private Sub Button2_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button2.Click
        End
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
    End Sub
End Class

Dim x As Double = 0.6
Dim eps As Double = 0.00001
Dim ff As Double = 1
Dim myCos As Double = 0
Dim i As Integer
Do While Math.Abs(ff) > eps
    i += 1
    myCos += ff
    ff = -ff * (x * x) / ((2 * i - 1) * 2 * i)
Loop
MsgBox("x=" & x.ToString & "; MyCos=" & myCos.ToString & " Cos=" & Format(Math.Cos(x), "0.######0"))