1.53: Cylinder with minimum surface area

0606/12/O/N/19 — Question 9 · 8 marks

A solid circular cylinder has a base radius of rr cm and a height of hh cm. The cylinder has a volume of 1200π1200\pi cm3^3 and a total surface area of SS cm2^2.
(i)
Show that S=2πr2+2400πrS = 2\pi r^{2} + \dfrac{2400\pi}{r}.
[3]
(ii)
Given that hh and rr can vary, find the stationary value of SS and determine its nature.
[5]