**Proposed exercise**

Calculate the perimeter, area and diagonal of a rectangle, given its width and its height.

(Hint: use y = Math.Sqrt(x) to calculate a square root)

**Output**

**Solution**

using System; public class Double { public static void Main() { double a, b; double area, perimeter, diagonal; Console.Write("Enter the width: "); a = Convert.ToDouble(Console.ReadLine()); Console.Write("Enter the height: "); b = Convert.ToDouble(Console.ReadLine()); perimeter = a*2 + b*2; Console.WriteLine("Perimeter: {0}", perimeter); area = a*b; Console.WriteLine("Area: {0}", area); diagonal = Math.Sqrt(a*a + b*b); Console.WriteLine("Diagonal: {0}", diagonal); } }