f '(u)= f '(g(x))= (f∘g)′(x)=
f(g) = tan(g) = tan(x^3) ... f'(g(x)) = 3x^2 sec^2(x^3) since (f∘g)(x) = f(g(x)) now I'm unsure just what you meant on the 2nd problem...
You can ask a new question or answer this question.