<Dl> <Dd> A = π a b . (\ displaystyle A = \ pi ab \, .) </Dd> </Dl> <Dd> A = π a b . (\ displaystyle A = \ pi ab \, .) </Dd> <P> The special case of a circle is ε = 0, resulting in r = p = r = r = a = b and A = πr . </P> <P> A line joining a planet and the Sun sweeps out equal areas during equal intervals of time . </P>

Referring to the path of a satellite around a planet