second. Note that when integrating along an axis other than the , the graph of the function that is farthest from the axis of rotation may not be that obvious. In the previous example, even though the graph of is, with respect to the x-axis, further up than the graph of , with respect to the axis of rotation the function is the inner function: its graph is closer to or the equation of the axis of rotation in the example. The same idea can be applied to both the -axis and any other vertical axis. One simply must solve each equation for before one inserts them into the integration formula. See also Solid of revolution Shell integration References Frank Ayres, Elliott Mendelson. Schaum's Outlines: Calculus. McGraw-Hill Professional 2008, . pp. 244–248 (. Retrieved July 12, 2013.) Integral calculus Volume