Find h' in terms of f' and g' if h(x) = f(g(cos(4x^{5}+lnx)))

I know h'(x) = f'g(x) . g'(x)

and I have g'(x) = -(20x^{4}+ 1/x)sin(4x^{5}+lnx) but does the f'g(x) mean that I must double differentiate or am i just interpreting it wrong and that's the answer?

y = ln (x.sqrt(x^{3}+2)/tanx) find dy/dx if possible. I would like to know if it exists and if so what conditions there are. I know for

y = ln(9-x^{2}) - ln(x-4) no differential exists due to the conditions of -3<x<3 and x>4

I also have no idea how to answer the following either:

Two cars, A and B, start moving from the same point P. Car A travels south at 60 km/h, while

Car B (the very slow driver!) travels west at 25 km/h. At what rate is the distance between the

cars increasing two hours later?

About how accurately should we measure the radius r of a sphere to calculate the surface area

S = 4 pi r^{2}to within 1% of its true value?