So let's just get to it. And this is just one of many proofs of the chain rule. So the chain rule tells us that if y, y is a function of u, which is a function of x, and we want to figure out the derivative of this, so we want to differentiate this with respect to x. So we're gonna differentiate this with respect to x. We could write this as the derivative of y with respect to x, which is going to be equal to the derivative of y with respect to u times the derivative of u with respect to x. This is what the chain rule tells us. But how do we actually go about proving it?