Calculating the distance between 2 points

Question

I have two points (x1,y1) and (x2,y2). I want to know whether the points are within 5 meters of one another.

Answer 1

Here is my 2 cents:

double dX = x1 - x2;
double dY = y1 - y2;
double multi = dX * dX + dY * dY;
double rad = Math.Round(Math.Sqrt(multi), 3, MidpointRounding.AwayFromZero);

x1, y1 is the first coordinate and x2, y2 the second. The last line is the square root with it rounded to 3 decimal places.