New approach to the plotting of phase-plane trajectories

By considering simultaneously the two planes x¿¿x¿ and x¿¿x, the isocline method is extended to find (for all initial conditions) the behaviour of second-order nonlinear autonomous systems which are not easily amenable to the usual phase-plane methods. The effect of variation of nonlinear functions can easily be studied. Simple as it is, the method is believed to be novel.