Thread: Mean curvature of a surface (just stuck with some simplifying!)

Hi everyone, new here and trying to calculate the mean curvature for the following surface:

r(u,v)=ui+f(u)cos(v)j+f(u)sin(v)k


I have been through the process of finding tangent vectors and a unit normal vector to the surface, so up to the point where I have had to substitute 6 scalars into:

h(p)=
aG-2bF-cE
2(EG-F²)

The only problem I seem to be having is not being able to simplify it... This is what I have:

h(p)=
± f''(u)f(u)²-f'(u)²-1
2f(u)(1+f'(u)²)√(cos²(2v)f'(u)+1)

Maybe missing something really simple here or I have made a mistake in calculating the scalars.

Any help, much appreciated!

(I have reposted this in University Maths - geometry, as it's in the wrong place.. any hints on how to delete this one though?)