void MethodCallOneOperand(string operation, TextBox res)
{
switch (operation)
{
case "sin":
res.Text = calculator.Sinus(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "cos":
res.Text = calculator.Cosinus(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "tan":
res.Text = calculator.Tangens(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "ctan":
res.Text = calculator.Cotangens(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "ln":
res.Text = calculator.NaturalLogarithm(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "invers":
res.Text = calculator.InverseNumber(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "sqr":
res.Text = calculator.Sqrt(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "squar":
res.Text = calculator.Squaring(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
case "factorial":
res.Text = calculator.Factorial(Convert.ToDouble(textBox_lastarg_or_answer.Text)).ToString();
break;
default:
break;
}
}