function(x, y) {
        return Math.atan2(
            this.x * y - this.y * x,
            this.x * x + this.y * y);
    }
function(x, y) {
        return Math.atan2(
            this.x * y - this.y * x,
            this.x * x + this.y * y);
    }
function ( x , y ) { return Math . atan2 ( this . x * y - this . y * x , this . x * x + this . y * y ) ; }
/*
Find the angle of the two vectors, solving the formula for
the cross product a x b = |a||b|sin(θ) for θ.
@param {Number} x the x-coordinate
@param {Number} y the y-coordinate
@return {Number} the angle in radians
/ * Find the angle of the two vectors solving the formula for the cross product a x b = |a||b|sin ( θ ) for θ .