Now let's just look and take a, let's just graph this or visualize this to get a sense of that. So this is our x-axis. Whoops, that's our x-axis. Let's call that our u-axis maybe. And I did u intentionally, because that's the variable we'll use in our proof of the chain rule video. And let's say this right over here is our function. Let's say this right over here, that is c. This right over here is u of c. u of c. And then let's just take some arbitrary x over here.