On the Limit Cycles of a Class of Planar Singular Perturbed Differential Equations

Figure 6

The graph of functions 𝜂₁(𝑢)/𝜂₂(𝑢) and 𝜂^′₁(𝑢)/𝜂^′₂(𝑢) on the interval (−1,0) are, respectively, plotted in solid line and point line.