#### Function Notation and Identities

- Many of the properties which have been investigated for the functions introduced in the previous chapters may be expressed using function notation.

- Below includes a few examples:

\ln x+\ln y=\ln (x y) becomes f(x)+f(y)=f(x y) where f(k)=\ln k

\ln x-\ln y=\ln \left(\frac{x}{y}\right) becomes f(x)-f(y)=f\left(\frac{x}{y}\right) where f(k)=\ln k