code: function(sin, cos) {
  
        var s = this['SCALE'];
        var angle = (1 + Math.acos(cos) / TAU) * s;
  
        if (sin < 0) {
          angle = s - angle;
        }
        return mod(angle, s);
      }
docs: Given the sine and cosine of an angle, what is the original angle?
  
  @param {number} sin
  @param {number} cos
  @returns {number}