Miscellany

// Inverse kinematic chain
// Set distance
var dist:Number = 100;
// Create a blank array to hold the positions of all your points
var points:Array = new Array();
// Populate the array, you could do this every frame and set each point as a movieClips x and y or whatever you need
for (var i:Number = 0; i<3; i++) {
	points.push([0, 0]);
}
onEnterFrame = function () {
	// Make first point = mouse x and y (or whatever you like)
	points[0][0] = _xmouse;
	points[0][1] = _ymouse;
	// Make the first point = a set point
	points[2][0] = 300;
	points[2][1] = 300;
	// Set distances every frame
	var ang:Number;
	for (var i:Number = 1; i<=2; i++) {
		ang = Math.atan2(points[i][1]-points[i-1][1], points[i][0]-points[i-1][0]);
		points[i][0] = points[i-1][0]+Math.cos(ang)*dist;
		points[i][1] = points[i-1][1]+Math.sin(ang)*dist;
	}
	// Draw lines between points
	_root.clear();
	_root.lineStyle(1, 0xFF0000, 100);
	_root.moveTo(points[0][0], points[0][1]);
	for (var i:Number = 1; i<3; i++) {
		_root.lineTo(points[i][0], points[i][1]);
	}
};