I wrote an app where we needed to get a list of properties within a radius of a given property, using lat/long coordinates. Given the search radius would be at

I wrote an app where we needed to get a list of properties within a radius of a given property, using lat/long coordinates. Given the search radius would be at most 5 miles, and didn't need to be 100% precise, I just treated the surface as a plane. A trivial solution to a trivial problem-- but it is neat to know the details of the formula for doing it precisely should I ever need it.