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Published online by Cambridge University Press: 31 October 2008
1. It is known that
(i) the line of striction of a ruled surface is the locus of points at which the geodesic curvatures of the orthogonal trajectories of the generators vanish,
(ii) if at each point of a curve C on a surface, a tangent to the surface is drawn, and these tangents generate a ruled surface of which C is the line of striction, then, if each tangent is turned through a constant angle α about its point of contact in the tangent plane, the new set of tangents also form a ruled surface with C as a line of striction.
1 See Forsyth, , “Differential Geometry,” p. 386.Google Scholar
2 See Richmond, , “A note upon some properties of the curve of striction,” Proceedings of the Edinburgh Math. Soc., 1923, p. 95Google Scholar, for a method of obtaining this result from geometrical considerations.
1 See Study, Geometrie der dynamen, p. 93Google Scholar; also Zindler, , Liniengeometrie, Vol. 31, p. 14.Google Scholar
2 Study, loc. cit., p. 303Google Scholar; Zindler, , loc. cit., p. 14.Google Scholar