Now let's figure out this derivative out here. So we want to find the derivative with respect to x of cosine e to the x. So once again, let me copy and paste it. So we need to figure out this thing right over here. So first, just like we did, we're just going to apply the chain rule again. We need to figure out the derivative of cosine of something, in this case, e to the x, with respect to that something. So this is going to be equal to derivative of cosine of something with respect to that something is equal to the negative sine of that something.