Show that if we had used regular perturbation to solve exercise 7.6.19, we would have obtained x{1, e)= a cost+ea f tsint+ cos 31 - cost)] +0(e) . why is this solution inferior? 7.6.19 (poincaré-lindstedt method) this exercise guides you through an improved version of perturbation theory known as the poincaré-lindstedt method. consider the duffing equation +x+ex'= 0, where 0