#include <cmath> using namespace std; // distance(x1, y1, x2, y2) returns the distance between // points (x1, y1) and (x2, y2) in the plane. double distance(double x1, double y1, double x2, double y2) { double deltaX = x1 - x2; double deltaY = y1 - y2; return sqrt(deltaX*deltaX + deltaY*deltaY); }