At each point [math]P[/math] on a circle of radius [i][math]r[/math][/i], a line segment is drawn perpendicular to the plane of the circle. The perpendicular segment at [math]P[/math] has length [i][math]ks[/math][/i] where [i][math]s[/math][/i] is the arc length of the circle from [math](r,0)[/math] to [i][math]P[/math][/i] and [i][math]k[/math][/i] is a positive constant. The collection of all these line segments forms the surface seen in this figure.

[i]Developed for use with Thomas' Calculus, published by Pearson.[/i]