code: function getVerticalFOV(hFov, aspectRatio) {
    var hFovRad = hFov * Math.PI / 180;
    var vFovRad = 2 * Math.atan(Math.tan(hFovRad / 2) / aspectRatio);
    return vFovRad * 180 / Math.PI;
  }
docs: Based on the code of http://themetalmuncher.github.io/fov-calc/