The Area ofa Surface of Revolution
Set up the integral for the area of the surface formed by revolving the graph of y=x^{3},\ 0\leq x\leq1, about the x-axis.
In this case, the radius is r(x) = x³ . Since f′(x) = 3x² , we have
S\;=\;2\pi\int_{0}^{1}x^{3}\sqrt{1+\left(3x^{2}\right)^{2}}\;d x\;=\;2\pi\int_{0}^{1}x^{3}\sqrt{1+9x^{4}}\;d x\;.
This integral can be calculated using substitution (u = x^{4} ) , and the answer is \frac{\pi}{27}\biggl(10^{\frac{3}{2}}-1\biggr)\approx3.563\,.