function ArrowHead(head_width, head_length) {
	var p1 = new Point(-head_length,-head_width/2);
	var p2 = new Point(-head_length,head_width/2);
	var p3 = new Point(0,0);
	this.superclass = Polygon;
	this.superclass([p3,p1,p2]);
	
	if (navigator.userAgent.indexOf('Opera') != -1)
		this.filled = false;
	else
		this.filled=true;
	
	this.putOn = function(line) {
		this.rotate(line.getAngle());
		this.translate(line.end.x, line.end.y);
	}	
}