So let's say this is some arbitrary x out here. So then this point right over there, this value, this y value, would be f of x. This graph, of course, is a graph of y equals f of x. And we can think about finding the slope of this line, this secant line between these two points. But then we can find the limit as x approaches C. And as x approaches C, this secant, the slope of the secant line is going to approach the slope of the tangent line, or it's going to be the derivative. And so we could take the limit as x approaches C, of the slope of this secant line. So what's the slope?