**Get inspired:**

**By the end of this lesson, you should be able to:**

- Explain what a conservative system is.
- Find a conserved quantity for a conserved system and use it to plot trajectories.
- Explain what a reversible system is and determine whether a system is reversible.
- Identify special cases where linear centers are guaranteed to be nonlinear centers

**Before class, please:**

- Read Strogatz, Sections 6.5 - 6.7.
- Read these notes.
- Check yourself before you wreck yourself (none)
- Participate in online community.

**In class, we will:**

- Conduction discussion, Q&A.
- Work on this activity (key).

**After class, please:**

- Do these problems.