It's one times negative one times x to the zero power, which is just one. So there you go. So we could view this as the derivative of secant with respect to u of x, and when we take the derivative, the derivative of secant with respect to u of x times the derivative of u with respect to x. And you might say, well what about the derivative of secant? Well in other videos we actually prove it out, and you could actually re-derive it. Secant is just one over cosine of x, so it comes straight out of the chain rule. So in other videos we prove that the derivative of the secant of x, is equal to sine of x over cosine of x over cosine of x squared.