One topic not covered in the aforementioned site is the derivatives of inverse functions...ok this is the best way I have discovered...I think it is right...it has always worked out before...I made it up so if its wrong I am sorry...$\displaystyle y=f(x)$...therefore $\displaystyle x=f(y)$ is the inverse....now taking the derivative we get $\displaystyle \frac{dx}{dy}=f'(y)$..but we want $\displaystyle \frac{dy}{dx}$...so....we reciprocate!....to get $\displaystyle \frac{dy}{dx}=\frac{1}{f'(y)}$