So this is one way to find the slope of the tangent line when x equals a. Another way, and this is often used as the alternate form of the derivative, would be to do it directly. So this is the point a comma f of a. Let's just take another arbitrary point, some here, some place. So let's say this is the value x. This point right over here on the function would be x comma f of x. And so what's the slope of the secant line between these two points?