Private Sub Command1_Click()
        Dim aa As Double ' Winkel Aplpha Text4
        aa = 0.095283018868
        Text4.Text = ArcCos(aa)
End Sub

Function ArcCos(z As Double) As Double
    If z = 1 Then
        ArcCos = 0
    Else
        ArcCos = 2 * Atn(1) - Atn(z / Sqr(1 - z * z))
    End If
End Function

fg viperbone