Public Class Form1
    '
    Dim ls As Double         ' Länge der Speichen
    Dim ads As Double        ' Anzahl der Speichen (36)
    Dim adk As Double        ' Anzahl der Kreuzungen (3)
    Dim df As Double         ' Durchmesser Felge (590)
    Dim bn As Double         ' Breite Nabe (71.6)
    Dim lk As Double         ' Lochkreis Nabe (40)
    '
    Dim df2 As Double        ' 590^2
    Dim bn2 As Double        ' 71.6^2
    Dim lk2 As Double        ' 40^2
    Dim alpha As Double      ' cosinus
    '
    Private Sub Rechnen_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Rechnen.Click
        '
        df = TextBox1.Text                      ' Innendurchmesser der Felge
        df2 = df * df                           ' df^2
        bn = TextBox2.Text                      ' Breite der Nabe
        bn2 = bn * bn                           ' bn^2
        lk = TextBox3.Text                      ' Lochkreis der Nabe
        lk2 = lk * lk                           ' lk^2
        adk = TextBox4.Text                     ' Anzahl der Kreuzungen
        ads = TextBox5.Text                     ' Anzahl der Speichen
        alpha = Math.Cos(720.0 * (adk / ads))   ' cosinus
        '
        '    l=√(0.25*(b^2 + D^2 + d^2) - (2 * D * d * cos(ß)))) <<- das 
        ' ist die original Formel.
        ls = Math.Sqrt(0.25 * (df2 + lk2 + bn2) - (2 * df * lk * alpha))     ' 
        ' Speichenlänge
        laenge.Text = ls
        '
    End Sub

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Man kann Dreck nicht polieren!
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