The table shows the latitude and longitude of three cities.
Earth is approximately a sphere with a radius of 3960 miles. The equator and all meridians are great circles. The circumference of a great circle is equal to the length of the equator or any meridian. Find the length of a great circle on Earth in miles.

| City | Latitude | Longitude
| A | 37°59'N | 84°28'W
| B | 34°55'N | 138°36'E
| C | 64°4'N | 21°58'W