Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As  _
      System.EventArgs) Handles btnDraw.Click
        seitea = Val(textbox1.Text)
        seiteb = Val(textbox2.Text)
        seitec = Val(textbox3.Text)
        Call dreieck(seitea, seiteb, seitec)
        Picturebox1.Invalidate()
    End Sub
 
    Sub dreieck(ByVal seitea As Double, ByVal seiteb As Double, ByVal _
        seitec As Double)
        summe = CSng((seitea + seiteb + seitec) / 2)
        TextBox4.Text = Math.Round(summe, 3)
        Return
    End Sub
 
    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As  _
      System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        Dim g As Graphics = e.Graphics
        g.Clear(Color.Yellow)
        g.DrawLine(Pens.Black, 100, 100, 200, 200)
        g.DrawLine(Pens.Black, CInt(summe), 100, 200, 200)
    End Sub