Код:
var speed:Number = 5;
var dx:Number = target._x - object._x;
var dy:Number = target._y - object._y;
var angle:Number = Math.atan2(dy, dx);
var vx:Number = Math.cos(angle) * speed;
var vy:Number = Math.sin(angle) * speed;
arrow._x += vx;
arrow._y += vy;