A Quick Word about Functions
This first chapter is about functions, which is the only true mathematical pre-requisite for calculus. As we will see in the definition of a function, functions are mathematical computer programs.
This chapter--like every chapter--begins with an example to help you discover the main idea of the chapter on your own. Then, in the middle of the chapter, the idea is defined formally. It's not a bad idea to jump ahead to the definition of a function to take a look now, but don't worry if it doesn't make sense. Come back to the start of the chapter, and work your way towards the definition, and by the time you get to the definition you will be prepared to understand it.
A note to people who have already taken calculus: If you already understand the concept of a function, I still think you should review how I define a function. Everything here is done quickly, and things are a little different than you might be accustomed to.