Well, that's just zero times the function on the bottom. So times cosine of x, cosine of x, minus, minus the function on the top, well, that's just one, times the derivative on the bottom. Well, the derivative of the bottom is, derivative of cosine of x is negative sine of x. So we could put the sine of x there, but it's negative sine of x, so you have a minus and there would be a negative, so we could just make that a positive. And then all of that over the function on the bottom squared. So cosine of x squared. And so zero times cosine of x, that is just zero.