The derivative of arccos(x)arccos(x) is d/dx(arccos(x))=-1/sqrt(1-x^2)ddx(arccos(x))=−1√1−x2 and we also know d/dx(e^(x))=e^(x)ddx(ex)=ex. We can combine these facts, as well as the Chain Rule (d/dx(f(g(x)))=f'(g(x))*g'(x)) to say that, for y=arccos(e^(4x)), we get