It is undefined when x is equal to c. And it even has a little kink in it just like that. And what we want to do is prove that the limit of f of x, and let me make it clear, this is the graph of y is equal to f of x. We want to get an idea for what this definition is saying if we're claiming that the limit of f of x as x approaches c is L. So conceptually, we get the gist already. We already get the gist that this right over here is L. But what is this definition saying? What's saying that you can get f of x as close to L as you want. So if you tell someone, I want to get f of x within a certain range of L, then if this limit is actually true, if the limit of f of x as x approaches c really is equal to L, then they should be able to find a range around c that as long as x is around that range, your f of x is going to be in the range that you want. So let me actually go through that exercise.