private void ArcCos(object sender, RoutedEventArgs e) { String inputDataA = tbA.Text; try { double dataA = Double.Parse(inputDataA); Trigonometry s = new Trigonometry(dataA); double result = s.ArcCos(); resultat.Text = result.ToString(); } catch (Exception) { MessageBox.Show("Numbers, Mayson, what are they meaning?..", "Error", MessageBoxButton.OK, MessageBoxImage.Error); } }