According to Equation (11.153),
According to Equation (11.154),
According to Equation (11.127),
Finally, according to Equations (11.130) and (11.142),
It follows from Equations (11.122)-(11.124), (11.159), (11.162), (11.174), (11.185), and (11.186), as well as the previous expressions for , , , , and , that the net perturbation to the lunar orbit due to the remaining terms in the solution of the lunar equations of motion is
All of the terms on the right-hand sides of Equations (11.332) and (11.333) are Keplerian in origin (i.e., they are independent of the perturbing influence of the Sun). The term on the right-hand side of Equation (11.332) is due to the slight inclination of the lunar orbit to the ecliptic plane, and is known as the reduction to the ecliptic.