private void Zaehnezahl_TextChanged(object sender, TextChangedEventArgs e)
        {
            double a = 0;
            double b = 0;
            double c = 0;
            double d = 0;


            if (Double.TryParse(Modul.Text, out a) && Double.TryParse(Zaehnezahl.Text, out b) && Double.TryParse(Schraegungswinkel.Text, out c))

                d = (a * b) / (System.Math.Cos(c * (Math.PI / 180)));

TextBox t = new TextBox();
t.Text = d;