Let
Take natural logs of both sides:
Use the fact that
Use the fact that to rewrite the last term:
Now finally we can take the derivative implicitly.
1. We use to take the
derivative of the term on the left.
2. is a constant so its derivative is 0.
3. We use for the last term
So for we take the derivatives:
Multiply both sides by
Use to replace
Rearranging the factors:
Replace by
Edwin