We know the derivative with respect to x of e to the x. E to the x is e to the x. We know how to find the derivative of cosine of x. The derivative with respect to x of cosine of x is equal to negative sine of x. But how do we find the derivative of their product? Well as you can imagine, this might involve the product rule. And let me just write down the product rule generally first. So if we would take the derivative with respect to x of the first expression in terms of x.