Thank you for your reply. My follow up question is
How did I know that I can't use "T" as the variable given that in the first equation I am taking a derivative with respect to "T" on the right hand side?
But I think I can see it if I work backwards:
where .
I know that at so
Next take the partial derivative of both sides with respect to "T" such that
by our earlier definition of .
Comments welcome. Thanks again