ABSTRACT
What the last section said for integrals, this section says for derivatives. If you remember nothing else from calculus, remember this: A derivative measures the slope of a tangent line. In particular, an increasing function must have a positive derivative. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9781315273976/51f4b530-0673-46a6-a3c6-73dbd21f9115/content/fig2_5_1_B.tif"/>
