求旋转角度的问题

    this.currentP = this.node.position;
    var p = this.currentP.sub(this.lastP);
    var rotationAngle = cc.pToAngle(p);
    this.node.rotation = rotationAngle;
    this.lastP = this.currentP;

这样处理还是不对。。。。。再次求教~