And when we say f prime of five, this is the slope, slope of tangent line, tangent line at five. Or you could view it as the, you could view it as the rate of change of y with respect to x, which is really how we define slope, with respect to x of our function f. So let's think about that a little bit. We see they put the point, the point five comma f of five right over here. And so if we want to estimate the slope of the tangent line, if we want to estimate the steepness of this curve, we could try to draw a line that is tangent right at that point. And so let me see if I can do that. So if I were to draw a line starting there, if I just wanted to make it tangent, it looks like it would do something like that, that right at that point, that looks to be about how steep that curve is. Now what makes this an interesting thing in nonlinear is that it's constantly changing.