public class Circle extends Shape
{
	private double radius;
	
	public Circle(double xCenter, double yCenter, double r)
	{
		super(xCenter, yCenter);
		radius = r;
	}
	
	public int numberOfSides() {
		return 0; //or infinite
	}
	
	public double area() {
		return Math.PI*radius*radius;
	}
	
	public double perimeter() {
		return 2*Math.PI*radius;
	}
}