Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim b As Double = 14.755            'm
        Dim gamma As Double = 90.20295      '°
        Dim soll_flaeche As Double = 12.42  'm²
 
        Dim Iterationen As Integer = 1
        Dim a As Double = 0.5               'Startwert
 
        Do Until Math.Abs(soll_flaeche - Calculator.Flaeche(a, b, gamma)) < 0.01
            Dim differenz As Double = soll_flaeche - Calculator.Flaeche(a, b, _
              gamma)
 
            If Calculator.Flaeche(a, b, gamma) < soll_flaeche Then
                Select Case differenz
                    Case > 1
                        a += 0.25
                    Case > 0.5
                        a += 0.1
                    Case > 0.25
                        a += 0.05
                    Case > 0.1
                        a += 0.01
                    Case > 0.01
                        a += 0.001
                End Select
            Else
                Select Case differenz
                    Case < -1
                        a -= 0.25
                    Case < -0.5
                        a -= 0.1
                    Case < -0.25
                        a -= 0.05
                    Case < -0.1
                        a -= 0.01
                    Case < -0.01
                        a -= 0.001
                End Select
            End If
            Iterationen += 1
        Loop
 
        Label2.Text = Math.Round(Math.Abs(soll_flaeche - Calculator.Flaeche(a, _
          b, gamma)), 3).ToString + Space(1) + "m²"
        Label4.Text = Calculator.C(b, a, gamma).ToString
        Label6.Text = Calculator.S(a, b, Calculator.C(b, a, gamma)).ToString
        Label8.Text = a.ToString
        Label10.Text = Iterationen.ToString
 
    End Sub

Public Class Calculator
    Public Shared Function C(ByVal loc_b As Double, ByVal loc_a As Double, _
      ByVal loc_gamma As Double) As Double
        Return Math.Sqrt((loc_a * loc_a) + (loc_b * loc_b) - (2 * loc_a * loc_b _
        * Math.Cos(loc_gamma * Math.PI / 180)))
    End Function
    Public Shared Function Flaeche(ByVal a As Double, ByVal b As Double, ByVal _
      gamma As Double) As Double
        Return Math.Sqrt(S(a, b, Calculator.C(b, a, gamma)) * (S(a, b, _
        Calculator.C(b, a, gamma)) - a) * (S(a, b, Calculator.C(b, a, gamma)) - _
        b) * (S(a, b, Calculator.C(b, a, gamma)) - Calculator.C(b, a, gamma)))
    End Function
    Public Shared Function S(ByVal loc_a As Double, ByVal loc_b As Double, _
      ByVal loc_c As Double) As Double
        Return ((loc_a + loc_b + loc_c) / 2)
    End Function
End Class

Public Shared Function Flaeche _
     (ByVal a As Double, b As Double, gamma As Double) As Double
 
     Dim cval As Double = Calculator.C(b, a, gamma)
     Dim sval As Double = S(a, b, cval)
     Return Math.Sqrt(sval * (sval - a) * (sval - b) * (sval - cval))
 
End Function

   Dim limits() As Double = {1, 0.5, 0.25, 0.1, 0.01, -0.0001}
   Dim adjust() As Double = {0.25, 0.1, 0.05, 0.01, 0.001, 0}
 
   sgn = Math.Sign(differenz)
   diff = Math.Abs(differenz)
 
   For i As Integer = 0 To limits.Length - 1
       If diff > limits(i) Then adj_value = adjust(i) : Exit For
   Next i
   adj_value *= sgn