Calculate Radius of a Circle in OpenLayers. Circle is implemented as a LinearRing.

gistfile1.js

OpenLayers.Geometry.LinearRing.prototype.getRadius = function() {
    //http://gis.stackexchange.com/questions/20982/how-to-get-the-radius-of-a-circle-in-openlayers
    //Use the formula for the area of a regular polygon.
    //With a radius of r and k vertices (where in practice k typically varies from 4 through 360),
    //the area now is A = r^2 * k Sin(360 / k) / 2. Solving for r yields r = Sqrt(2 A / (k Sin(360/k))).
    //For k = 40 that's r = 0.565352 * Sqrt(A).
    var area = Math.abs( this.getArea() );
    var polygonSides = 100;
    var radius = Math.sqrt( 2*area/(polygonSides*Math.sin(2*Math.PI/polygonSides)) );
    return radius;
}