Help squaring a variable

[yoda493]

I want to square a variable. Please help me.Here is my code:

code:

decimal number1 = Convert.ToInt32(textBox1.Text);
double pi = Math.PI;
double Radius_to_Circumference = (double)number1 * 2 * pi;
double RTD = (double)number1 * 2;
double RTA = (double)Math.Pow(number1, 2) * pi;
MessageBox.Show("The circumference is " + Radius_to_Circumference + " \nThe Diameter is " + RTD + " \nThe Area is " +;