In particular, let's see if we can figure out what the derivative with respect to x of the inverse tangent of x is. I encourage you to pause this video and use a technique similar to the one, or very close to the one, that we've used in the last few videos to figure out what this is. Let's set y equal to the inverse tangent of x. y is equal to inverse tangent of x. That is the same thing as saying that the tangent of y is equal to x. All I've done is, you can kind of think of it as, I've just taken the tangent of both sides right over here. Now we can take the derivative of both sides with respect to x. On the left-hand side, we can just apply the chain rule.