And then he says, okay, well, this is gonna be the same thing as the derivative, or this is the same thing as the product of the derivatives. Now this is a problem. You are probably familiar, if I take the derivative of the sum of two things, so the derivative with respect to x of f of x plus g of x, that indeed is equal to the derivative of the first, f prime of x, plus the derivative of the second. But that is not true if we are dealing with the product of functions. The derivative with respect to x of f of x, g of x, is not necessarily, maybe there's some very special circumstances, but in general, it's not going to be just the product of the derivative. It's not going to be just f prime of x, g prime of x. Here we would want to apply the product rule.