<Dd> a = r max + r min 2 . (\ displaystyle a = (\ frac (r_ (\ max) + r_ (\ min)) (2)).) </Dd> <P> The semi-minor axis of an ellipse is the geometric mean of these distances: </P> <Dl> <Dd> b = r max r min . (\ displaystyle b = (\ sqrt (r_ (\ max) r_ (\ min))).) </Dd> </Dl> <Dd> b = r max r min . (\ displaystyle b = (\ sqrt (r_ (\ max) r_ (\ min))).) </Dd>

Semi major and semi minor axis of earth