"This class of spirals may be generated by unwinding a perfectly flexible but inextensible chord from a polygon of any number of sides, the names of the involutes being derived from the polygons which determine their form. The curves consist of radii increasing by an amount equal to the length of the sides." —Anthony, 1904

Involute Spiral

"This class of spirals may be generated by unwinding a perfectly flexible but inextensible chord from…