What this is, if we had f of x is equal to log of x, and we wanted to know what f prime of, well actually, let's say f prime of two is, well, this would be the limit as h approaches zero of log of two plus h, two plus h, minus log of two, minus log of two, all of that over h. So this is really just a, what we see here, this by definition, this right over here is f prime of two. If f of x is log of x, this is f prime of two. F prime of two. So can we figure that out? If f of x is log of x, what is f prime of x? F prime of x, we don't need to use the limit definition. In fact, the limit definition is quite hard to evaluate this limit, but we know how to take the derivative of logarithmic functions.