Young, George, jr, Baxter, Hubert Eugene, joint author · New York, Macmillan · leaf 198
is evident that hg and ch are lines in the same plane, as arealso ch and di. But if the points a and d are not in the same plane, it isevident that the lines hg and di are not in the same plane.Nevertheless the surface afje is developable, since it is com-posed of plane elements, as in the case of… … Fig. 171 tangent; and the series of plane surfaces approaches a develop-able ruled surface. This evidently means that such a surfacemay be generated from any space curve. Such a surface as described above, being a developable ruledsurface, is most closely related to the cone and cylinder in…
Geometry, Descriptive
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