We're gonna take the derivative of that with respect to u, which is just cosine of x, and we're gonna multiply that times the derivative of u, which is cosine of x, with respect to x, so this one we have good, we've seen this before. We know that the derivative with respect to x of cosine of x, cosine, let me use it in that same color, the derivative of cosine of x, well that's equal to negative sine of x. So this one right over here, that is negative sine of x. You might be more familiar with seeing the derivative operator this way, but in theory, you won't see this as often, but this helps my brain really grok what we're doing. We're taking the derivative of cosine of x with respect to x, well that's gonna be negative sine of x. Well what about taking the derivative of cosine of x to the third power with respect to cosine of x? What does this thing over here mean?