It's not just x-y coordinates; it's x-y-z coordinates that you need. The cities are on the surface of the earth, so they are one earth's radius from its center. Lattitude and longitude give you the rest of the information you need to express the postions of the cities in terms of x-y-zcourtrigrad said:So if the question is: A man flies from Washington to Manilla. Find the magnitude of the displacement vector if the latitudes and longitudes are: 36 N, 70 E, 121 N, 56 W. You would have to convert the latitudes and longitudes into x-y coordinates? How would you do that?