The current example of stability in Ch 5 (dynamics) uses a linear system with purely circular trajectories to illustrate a center. If we change the second equation from
\dot x_2 = -x_1
\dot x_2 = -\lambda x_1
Then the circles will change to ellipses and this might be more illustrative. We should think about this as a possible change in the main text, but if it is too disruptive then it could just be an exercise. Main goal is to get something where $\epsilon$ and $\delta are different.