Get distance between two coordinates

getdistance.js

//get distance between two geo coordinates in kilometers
function distanceInKilometers(lat1, lon1, lat2, lon2) {
    var rlat1 = Math.PI * lat1/180
    var rlat2 = Math.PI * lat2/180
    var rlon1 = Math.PI * lon1/180
    var rlon2 = Math.PI * lon2/180
    var theta = lon1-lon2
    var rtheta = Math.PI * theta/180
    var dist = Math.sin(rlat1) * Math.sin(rlat2) + Math.cos(rlat1) * Math.cos(rlat2) * Math.cos(rtheta);
    dist = Math.acos(dist)
    dist = dist * 180/Math.PI
    dist = dist * 60 * 1.1515
    dist = dist * 1.609344
    return dist
}
//get distance between two geo coordinates in miles
function distanceInMiles(lat1, lon1, lat2, lon2) {
    var rlat1 = Math.PI * lat1/180
    var rlat2 = Math.PI * lat2/180
    var rlon1 = Math.PI * lon1/180
    var rlon2 = Math.PI * lon2/180
    var theta = lon1-lon2
    var rtheta = Math.PI * theta/180
    var dist = Math.sin(rlat1) * Math.sin(rlat2) + Math.cos(rlat1) * Math.cos(rlat2) * Math.cos(rtheta);
    dist = Math.acos(dist)
    dist = dist * 180/Math.PI
    dist = dist * 60 * 1.1515
    dist = dist * 0.8684
    return dist
}

// some examples
Math.round(distanceInKilometers(56.834167,60.600105, 56.837699,60.599051)*100)/100
//0.4 - this is correct
Math.round(distanceInKilometers(56.836127,60.599538, 56.837733,60.599034)*100)/100
//0.18 - this is correct