using System;

​

class Circle

{

    private double radius;

​

    public Circle()

    {

        radius = 0;

    }

​

    public Circle(double radius)

    {

        this.radius = radius;

    }

​

    public double GetArea()

    {

        return Math.PI * radius * radius;

    }

​

    public double GetCircumference()

    {

        return 2 * Math.PI * radius;

    }

​

    public double GetSectorArea(double angle)

    {

        return (angle / 360) * GetArea();

    }

}

​

class Sphere : Circle

{

    public Sphere() : base()

    {

    }

​

    public Sphere(double radius) : base(radius)

    {

    }

​

    public double GetSurfaceArea()

    {

        return 4 * GetArea();

    }

​

    public override double GetArea()

    {

        return 4 * Math.PI * base.GetArea();

    }

​

    public override double GetCircumference()

    {

        return 2 * Math.PI * base.GetRadius();

    }

}

Circle circle = new Circle(5);

Console.WriteLine("Circle area: " + circle.GetArea());

Console.WriteLine("Circle circumference: " + circle.GetCircumference());

Console.WriteLine("Sector area (30 degrees): " + circle.GetSectorArea(30));

​

Sphere sphere = new Sphere(5);

Console.WriteLine("Sphere area: " + sphere.GetArea());

Console.WriteLine("Sphere surface area: " + sphere.GetSurfaceArea());

Console.WriteLine("Sphere circumference: " + sphere.GetCircumference());