code: function getRadius(latRadians) {
    var cos, sin, t1, t2, t3, t4;
  
    cos = Math.cos(latRadians);
    sin = Math.sin(latRadians);
    t1 = RADIUS_EQUATOR * RADIUS_EQUATOR * cos;
    t2 = RADIUS_POLES * RADIUS_POLES * sin;
    t3 = RADIUS_EQUATOR * cos;
    t4 = RADIUS_POLES * sin;
  
    return Math.sqrt((t1 * t1 + t2 * t2) / (t3 * t3 + t4 * t4));
  }
docs: Determines radius
  
  @param {Number} latRadians
  @returns {Number}