Let me paste it. So times the derivative with respect to x of all of that. And now the fundamental theorem of calculus directly applies. This is going to be equal to, we deserve a drum roll now, this is going to be equal to the negative. Can't forget the negative. And the fundamental theorem of calculus tells us that that's just going to be this function as a function of x. So it's going to be negative square root of the absolute value of cosine of not t anymore, but x.