Ans:

Our class extends the Sprite class which means that any instance of TriangleBoard will be a Sprite and will inherit all the methods and properties of the Sprite class. It will also have additional properties and methods that we define within the class.

for example:

public class TriangleBoard extends Sprite {    
private var shTriangle:Shape;    
private var spPoint1:Sprite;    
private var spPoint2:Sprite;    
private var spPoint3:Sprite;    
private var boardWidth:Number;    
private var boardHeight:Number;    
private var colorBack:Number;   
private var colorBorder:Number;    
private var colorDot:Number;    
private var colorTriangleBorder:Number;    
private var colorTriangleFill:Number;    
private var radiusDot:Number;    
private var numPoints:int;      
.......................    
.......................    
}