1.13 In Exercise 3.9 of Chapter 1 the pendulum problem was scaled to obtain the initial value problem 220 sin A0 + 0, > 0, 0<A<<1 dr² A de 0(0)-1, -(0) -0 dr Apply the regular perturbation method to find a two-term expansion. Show that the correction term is secular and comment on the validity of the approximation.