What you have to do here is show that the derivative of:Originally Posted by wcwalberg
and that .
The second of these is trivial; just plug in place of in the
definition of to find .
For the first part you need to differentiate:
to find . To do this you need to use
the product rule on the first term on the RHS (the second term is a
constant and so has derivative ):
Here we let , and , then
and the result should follow.