As f(x) is in the form of u(x)/v(x) we can apply the rule that f'(x) = (u'(x)*v(x) - v'(x)*u(x))/(v(x)2), pulled from the C3 formula booklet.
If u(x) = sin(2x) then u'(x) = 2cos(2x).
If v(x) = x2 then v'(x) = 2x.
Hence, f'(x) = ((2cos(2x)*x2) - (sin(2x)*2x))/(x4)
(Will be easier to explain on a whiteboard w/ standard visualisation of functions)