Today we kept the lecture short and sweet due to the quiz. We reviewed the idea of inverse functions, functions that "reverse" the action of a given function. We recalled that the functions with an inverse were exactly the one-to-one functions. Just as a graph is the graph of a function if it passed the vertical line test, a function is one-to-one if and only if its graph passes the horizontal line test. (Those are the tests that say a graph is the graph of a function (a one-to-one function) if no vertical (horizontal) line touches the graph in more than one point.)

We also recalled how to find a formula for the inverse of a one-to-one function. (It can't always be done due to the algebra difficulty.) We also recalled how to graph an inverse, even if we don't have a formula in hand.

Then we took the quiz. Friday, we'll talk about exponentials, logarithms, and maybe even trig functions.