In this map, the origin is set at Hong Kong. 1 unit represents 800 km. [br][br]A cyclone C is travelling along the path from A to B. What is the position of C when it is 800 km (that is 1 unit) away from Hong Kong? (Use the slider d to see the movement of C.)[br][br]In general, we may use coordinates to tell the position of a point (such as the cyclone C). How can the coordinates tell us whether a point is 1 unit from the origin? Add more points on the map to test your method.[br]