The traditional Kepler problem of calculating the orbit of an inverse square law may be read off from the Binet equation as the solution to the differential equation − − k u 2 = − − m h 2 u 2 ( d 2 u d θ θ 2 + u ) d 2 u d θ θ 2 + u = k m h 2 ≡ ≡ constant > 0.