Как считать интеграл и сохранять его в "таблицу"? - Visual Basic .NET

Public Class Form1
    Private xmin, xmax, ymin, ymax, w, h As Integer
    Private bmp As Bitmap
    Private g As Graphics
    Private pnAxis, pnGraphics As Pen
    Private pnt As List(Of PointF), pp As PointF
    Private isDraw As Boolean
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        xmin = -7 : xmax = 7 : ymin = -2 : ymax = 2
        w = PictureBox1.Width
        h = PictureBox1.Height
        bmp = New Bitmap(w, h, PictureBox1.CreateGraphics())
        PictureBox1.Enabled = False
        pnAxis = New Pen(Brushes.Blue, -1)
        pnGraphics = New Pen(Brushes.Red, 2)
        Button1.Enabled = False
        Label2.Text = "min = " & xmin.ToString
        Label3.Text = "max = " & xmax.ToString
        Label5.Text = "min = " & ymin.ToString
        Label4.Text = "max = " & ymax.ToString
        Label1.Text = "X"
        Label6.Text = "Y"
        Label7.Text = "Интегралл"
        Label8.Text = ""
    End Sub
    Private Sub CreateGraphics_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        PictureBox1.Enabled = True
        gettingStartedCanvas()
        Button1.Enabled = True
        Label8.Text = ""
    End Sub
    Private Sub GetIntegral_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim kx As Double = w / 2 / xmax
        Dim ky As Double = h / 2 / ymax
        Dim p As PointF
        For i = 0 To pnt.Count - 1
            p = pnt(i)
            p.X -= w / 2
            p.Y -= h / 2
            p.Y = -p.Y
            p.X /= kx
            p.Y /= ky
            pnt(i) = p
        Next
        'вычисляем приближенно по методу трапеций
        Dim sum As Double = 0.0
        For i = 1 To pnt.Count - 1
            sum += (pnt(i - 1).Y + pnt(i).Y) / 2 * (pnt(i).X - pnt(i - 1).X)
        Next
        Label8.Text = sum.ToString
        Button1.Enabled = False
        PictureBox1.Enabled = False
    End Sub
    Private Sub gettingStartedCanvas()
        g = Graphics.FromImage(bmp)
        g.Clear(PictureBox1.BackColor)
        g.DrawLine(pnAxis, New Point(w / 2, 0), New Point(w / 2, h))
        g.DrawLine(pnAxis, New Point(0, h / 2), New Point(w, h / 2))
        PictureBox1.Image = bmp
        g.Dispose()
    End Sub
    Private Sub PictureBox1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        Dim x As Integer = e.Location.X
        Dim y As Integer = e.Location.Y
        If x <> 0 Then x = 0
        pnt = New List(Of PointF)
        pp = New PointF(x, y)
        pnt.Add(pp)
        isDraw = True
        g = Graphics.FromImage(bmp)
    End Sub
    Private Sub PictureBox1_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        If Not isDraw Then Exit Sub
        Dim x As Integer = e.Location.X
        Dim y As Integer = e.Location.Y
        If x <> w Then x = w
        pnt.Add(New PointF(x, y))
        g.DrawLine(pnGraphics, pp, pnt(pnt.Count - 1))
        isDraw = False
        g.Dispose()
        PictureBox1.Image = bmp
    End Sub
    Private Sub PictureBox1_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If isDraw Then
            Dim x As Integer = e.Location.X
            Dim y As Integer = e.Location.Y
            If x <= pp.X Then Exit Sub
            Dim p As PointF = New PointF(x, y)
            g.DrawLine(pnGraphics, pp, p)
            pnt.Add(p)
            pp = p
            PictureBox1.Image = bmp
        End If
    End Sub
End Class