**Learning objectives**

- Interpret second derivatives
- Measure change two ways: absolute change and relative (percent) change
- Understand relative rates (such as birth rates)
- (percent change in ) (rel derivative)
- rel derivative

- Understand elasticity (such as price elasticity of demand)
- (percent change in ) (elasticity) (percent change in )
- elasticity

**Before class**

- Read Hughes-Hallett 2.3 (relative rate of change), 2.4, 4.6
- Ponder problems 2.3. 42, 43, 44, 46; 2.4. 2, 10, 20, 26; 4.6. 1, 2, 3, 4.
- Consult the main points of the lesson.
- Consult notes on two types of change and three derivatives. Focus on the summary at the end.

**.In class**