(a)
(b)
(c)
(d)

Figure 2: Subgraphs (a), (b), and (c) show the solutions of (15) with an initial value near , , and , respectively. Subgraph (d) displays the solution of (15) with an initial value near . It can be observed that is stable and is unstable for . Subgraph titles clarify the initial points of system (15). The parameters are set as follows: , and .