<Dl> <Dd> R m = 2 1 M + 1 N (\ displaystyle R_ (\ mathrm (m)) = (\ frac (2) ((\ dfrac (1) (M)) + (\ dfrac (1) (N)))) \, \!) </Dd> </Dl> <Dd> R m = 2 1 M + 1 N (\ displaystyle R_ (\ mathrm (m)) = (\ frac (2) ((\ dfrac (1) (M)) + (\ dfrac (1) (N)))) \, \!) </Dd> <P> The Earth can be modeled as a sphere in many ways . This section describes the common ways . The various radii derived here use the notation and dimensions noted above for the Earth as derived from the WGS - 84 ellipsoid; namely, </P> <Dl> <Dd> a = Equatorial radius (7006637813700000000 ♠ 6378. 1370 km) </Dd> <Dd> b = Polar radius (7006635675230000000 ♠ 6356. 7523 km) </Dd> </Dl>

Which of the following of earth's radii is greater