Finding a coordinate in a circle

Question

I am doing a mashup using Google Maps under Grails where users can create geofences by selecting a point on the map and a radius. This get stored on my database and the appl

Answer 1

You want to find the vector that is the distance between the selected coordinate and the center of the circle, then compute the square distance between the selected coordinate and the center of the circle by squaring the components of the vector and adding them together; if that scalar (the squared distance) is less than the square of the radius, the point is within the circle.

This method avoids having to take a square root, and is just as accurate as normal distance comparison.