Question

f(x)=tan^2(x^3+1)....f'(x)=?

Answer 1

I believe that you need to use the Chain Rule for that one.
Try this:
f(x)=tan^2(x^3+1)
Let u=tan(x^3+1)
.: f(x)=u^2
.: f '(x)=2 * u * (derivative of u)
And I'm sure you can do the rest.