9231 P1 - Jun 2009 - Q4
6569
A curve has equation
\(y=\frac{1}{3} x^{3}+1 .\)
The length of the arc of the curve joining the point where \(x=0\) to the point where \(x=1\) is denoted by \(s\). Show that
\(s=\int_{0}^{1} \sqrt{ }\left(1+x^{4}\right) \mathrm{d} x\)
The surface area generated when this arc is rotated through one complete revolution about the \(x\)-axis is denoted by \(S\). Show that
\(S=\frac{1}{9} \pi(18 s+2 \sqrt{ } 2-1) .\)
[Do not attempt to evaluate \(s\) or \(S\).]
